FDR is also far older than any of this UAC history. Perhaps this was a case of noisily shutting the barn door after the horses were not just fled but out of sight?
I say again the problem is not anything other than that Christianity faded back. Perhaps it had been spoiled by being protected by sheer popularity. The result was that it knew, at best, only how to fight trivial devils, like smoking and gambling and cussing etc.
Subversive elements investigative committees began as far back as 1918.
But the leftist element realized that if you got control of the government, you could start to transform the country (along with getting control of education and entertainment industries). This pre-dated FDR, but the Great Depression (which was willfully exacerbated by FDR and his failed policies) gave a lot of impetus to begin to remove private-sector and Christian solutions to problems and place them more in the realm of government control. Those that stood in the way of that transfer of massive government expansion had to be removed.
I’ve often cited the case of Black GOP Congressman Oscar De Priest of Chicago. He was bitterly opposed to the fledgling welfare state policies of FDR, because he believed they would be utterly devastating to the Black Community (at the time, he was the only Black Congressman. The Dems had disenfranchised Southern Blacks, who would’ve sent several more members from that region, all Republican). He knew those programs/policies were designed to breed dependence and would literally enslave vulnerable Blacks in short order. He was prophetic, of course. But the Dems worked very hard to remove him from office, and were successful in the 1934 midterms (he tried to get back the office, but failed).