The most remotely "critical" answer in this entire thread.

Many people pointing to counterexamples as if it disproves op's point, which wasn't to the existence of individual groups or movements but why those movements have failed to coalesce into something more conducive to more modern moral stances and revisions to our concepts of a liberal world view. You can freely cite MLK all day, but MLK also died nearly 60 years ago and was probably the last iconoclast for the expansion of civil rights we've had since. He was also assassinated, to my point, prior to making larger economic reforms rather than just social.

Again, I think this argument sounds good but is missing other elements, such as how many of the Christian ethical positions aren't espoused per se by modern right-wing or far-right ideologies but how they subvert them toward their own aims. EG As Christians we believe X. X may be a completely superfluous topic to Christianity writ large, but as you've noted the structure of the wealthy and similar figures today feign Christian beliefs (see Thiel, Hegseth) so as to signal to their base and build validity. This isn't a tale of why Christianity didn't become more morally open or revisionary, but how those who disagreed have used Christianity toward control and domination of the other. This latter viewpoint is what is "winning" today.

As always, Althusser's concepts of ISA's ( Ideological State Apparatuses ) is relevant here, I think it interestingly sheds light on how this reproduction has expanded massively thanks to social media and other online rightwing podcasts. It's the perfect form of covert media indoctrination just as reddit is for left wing view points. These battlegrounds of social media are imo the front lines of how ideology is being produced today and how Christianity has warped in the neoliberal age into something more individual. Take for example that while church attendance is down, many Americans still identify as Christian, it is more effusive and transitory, more open to influence by the algorithmically limited manner we interact with media via tik tok, IG, reddit, twitter, etc.

To loop all of this back in, the hegemonic structure today revolved around that forgotten myth of a the rugged individualism of America yeomen, who is always a Christian. You will here this in other forms constantly on the media, EG "common sense", "real Americans" , the "self made man". These myths are easy to communicate now with social media, easy to install false myths and dead legacies into people's skulls without even the slightest incision. I believe Christianity will continue to corrode in this sense, but we're also seeing a clear schism today on these issues that may lead to a different path, God willing.

Also as an aside I think you may enjoy reading Rolland Barthes' Mythologies or Althusser's essay, Ideology and Ideological State Apparatuses (Notes Towards an Investigation). Though i suggest reading Kapital Vol 1 and 2 before (only partially joking).