Because it's an article of faith for hard money enthusiasts[1] that nearly all society's economic ills can be blamed on the abandonment of the last vestiges of the gold standard, which happened in 1971, and yet anyone who pays any attention to the posted charts will notice that 1971 isn't actually the inflection point or even a partiocularly notable date on many of them. As you point out, there are many other historically pivotal things in the mid-late twentieth century that caused systemic changes, and many of those timelines better fit the data.

[1]A cursory look at the site's blog posts will confirm the site author is indeed one https://wtf1971.com/page/2/