Were modern wheat varieties specifically selected because it was less nutritious?
tl;dr: Surely not.
How were wheat cultivars bred?
For what did breeders select?
Was the nutritional value monitored, cared for, or ignored, or even systematically reduced?
If one answers these questions the picture is very clear.
This claim constructs a capitalist conspiracy were there is none. The first Green Revolution of the sixties had its problems and still has: it was entirely focused on industrialised, mechanised, chemicalised agriculture, then seen as the future and without alternative, disregarding several consequences. But the general aim in that revolution was to end world hunger and starvation! And of course to make a buck in the process. But providing more nutrition is not achieved by reducing the nutritional value of a crop.
For the first green revolution, which saved Asia from hunger in the 1960s, was not built on new knowledge but on the adaptation of principles derived from earlier research.
Earlier goals to increase yield increased the height of wheat so that it outgrew unwanted weeds. Much energy is therefore "wasted" in not going into the fruit but the stem and leaves. The height brings another problem in increasing the danger of weather events destroying the crop which might bend, break, fall more easily. The second use scenario as building material really is secondary when growing foodstuff.
In this 60s revolution semi-dwarfing genes were introduced to address both problems of waste: lower height means more energy for producing nutritious grain and lower risk of loss to breaking. The problem of weed competition was already solved: herbicides! (That is of course a whole new can of worms, not covered in this answer)
Following incorporation of semi-dwarfing genes, wheat production doubled in the 1960s, an era called the Green Revolution. The Green Revolution resulted in the development of semi dwarf wheat cultivars that were highly responsive to inorganic fertilizer application, were early maturing and resistant to lodging. Semi dwarf cultivars also remained resistant to various diseases for many decades. Wheat genetic gains are less than 1 % per annum which are not sufficient to meet the future food demand of ever increasing human population.
As for the nutritional value:
Grain protein content determines the nutritional value of wheat grain, as well as the rheological and technological properties of wheat flour (Zhao et al. 2010). The wheat quality of bread making is associated with the absence or presence of specific proteins and their subunits (Dhaliwal et al. 1994; Payne et al. 1987; Snape et al. 1993). In addition, bread making quality also depends on the proportion of polymeric and monomeric proteins, and the amount and size distribution of the former (Gupta et al. 1993). The endosperm proteins have a key role in the determination of wheat quality. The four major types of endosperm proteins in wheat include Prolamines, Albumins, Gliadins, and Glutenins (Gupta et al. 1992). Payne et al. (1987) reported that glutenin protein content and composition control most of the variation in wheat flour quality. Glutenins account for 80 % of wheat proteins and are the principal components that determine dough quality (Payne et al. 1987). Gliadins and glutenins are wheat storage proteins and are the principal components of wheat gluten. Gluten proteins give unique viscoelastic properties to the wheat flour. Glutenins are polymeric proteins with disulphide bonds connecting the individual glutenin subunits. Glutenin subunits are further subdivided into low molecular weight (LMW-GS) and high molecular weight (HMW-GS) subunits. LMW-GS have molecular weight of 23–68 k Da, whereas HMW-GS are from 77 to 160 k Da. In addition to molecular weight, these two subunits also differ from each other in their structure and amino acid composition (Branlard et al. 1989).
While gluten is now often seen as problem in itself, for most people it is not. It has the utmost importance for the perceived quality of bread made from wheat and it was therefore a primary goal to increase in breeding. The rise in or increased awareness for celiac disease was unforeseen at the time and the current trends in hysteria are not really connecting to breeding programmes in the sixties either.
These wheat cultivars that were introduced in the Green Revolution have their problems. When they are used in an organic setting, it is revealed that they are heavily dependent on the setting for which they were developed: industrialised farming. Without fertiliser, herbicides and on marginal land, these cultivars decrease in yield. In organic settings older or different types have to be selected as a matter of necessity. The supposedly less nutritional semi-dwarfs would be suicide, in all views: economical, nutritional etc. So, how do they compare:
In a long-term (21 years) study, Maeder et al. (2007) reported no difference in nutritional value (amino acid compositions, protein content, mineral contents, and trace element contents) and baking quality of wheat grains in organic and conventional systems. Similar findings in terms of grain protein content (Shier et al. 1984) and nitrogen concentration (Ryan et al. 2004) have also been documented. The environment was reported as the major driver of variation in protein content (Fowler and Delaroche 1975) along with nitrogen fertilizer and soil moisture content (Preston et al. 2001; Shier et al. 1984). With the application of nitrogen fertilizer, an increase in grain protein content and gluten strength has been reported in various studies (Ames et al. 2003; Gooding et al. 1993; Johansson et al. 2003; Lerner et al. 2006). Mazzoncini et al. (2007) reported 20 % less protein content of grain samples from organic than conventionally managed systems. They further reported poor bread making quality of organic samples; however, there were no visual differences for crumb volume and crust thickness. Similar findings of higher grain protein content of wheat grown in conventional management system have also been reported in various other studies (Baeckstrom et al. 2004; Starling and Richards 1993).
Depending on the exact definition of "nutritional value", starch and protein are by far the most important factors, but not the only ones. An often cited study as "proof for decreased nutritional value" is focusing on the (trace) minerals Evidence of decreasing mineral density in wheat grain over the last 160 years (2008):
Abstract: The concentrations of zinc, iron, copper and magnesium remained stable between 1845 and the mid 1960s, but since then have decreased significantly, which coincided with the introduction of semi-dwarf, high-yielding cultivars. In comparison, the concentrations in soil have either increased or remained stable. Similarly decreasing trends were observed in different treatments receiving no fertilizers, inorganic fertilizers or organic manure. Multiple regression analysis showed that both increasing yield and harvest index were highly significant factors that explained the downward trend in grain mineral concentration.
Reading it reveals the following:
Our results show that the decreasing mineral concentrations in wheat grain are partly due to a "dilution" effect resulting from increased yield. […]
It thus appears that changes in cultivar are a key determinant of the relationship, or lack of it, between grain yield and mineral concentrations. This is further supported by the fact that increasing HI, as a result of the introduction of short-straw cultivars, also contributed significantly to the decreasing trends in grain mineral concentrations. Dwarfing of wheat cultivars is achieved by the introduction of the gibberellin-insensitive Rht genes; as a result, proportionally more photosynthates are distributed to the grain. It is unlikely that the dwarfing genes would have a pleiotropic effect on the uptake of several mineral nutrients from the soil. A more plausible explanation is that the re-distribution of minerals from the vegetative tissues to grain does not catch up with the much enhanced re-distribution of photosynthates in the short-straw cultivars.
Note that the average wheat eater normally doesn't care much about minerals, discarding most of them anyway with much of the fibre when making flour.
The claim is beyond ridiculous. It never was a goal in breeding to reduce the nutritional value of wheat. If it would have been a goal to reduce the nutritional value then breeders seem to have failed in reaching that goal.
F. G. H. Lupton: "Wheat Breeding. Its Scientific Basis", Springer: Dordrecht, 1987.
Muhammad Asif, Muhammad Iqbal, Harpinder Randhawa, Dean Spaner: "Managing and Breeding Wheat for Organic Systems. Enhancing Competitiveness Against Weeds", Springer: Cham, Heidelberg, 2014.