New Atheism was a tool used by the Left and Progressive movement to attack one of the core constituents of the American Right. Once they were no longer useful for that, which they rapidly became since, they have been discarded.
To be frank, the "new atheist" critique of Christianity was nothing new and was mainly just popularizing and rehashing old arguments. I'll be honest, I never saw a "New Atheist" critique of religion or Christianity that was new or that had not been answered by Christian apologetics numerous times over in the past. It's success mainly came in that much of the American Christian Church had systemically failed to educate it's membership in apologetics, and so most of it's success came when arguing against those who were not educated on those answers. Plus they were propped up by the media who saw them as useful pawns against those on the right.
Once the New Atheists became a risk of driving away Muslim voters, whom were seen as a more rapidly growing demographic than atheists, plus with the rise of Intersectionality as the driving ideology of the Left (whom the main proponents of New Atheism failed to have high standing in), you saw the movement splinter.
What's been very interesting to me is the number of people who were formally New Atheists whom did not buy into Intersectionality and how they've slowly come to understand the value of Christianity in western civilization over time. There's been quite a number who have turned around and said that while they still are atheists, they regret going so hard against Christianity as it has become clear that a lot of the foundational values of the west were founded in it, and without that foundation, things get ugly.
Thus, in some ways, the New Atheist movement was splintered by the rise of Intersectionality. Intersectionality likely absorbed the majority of the New Atheists, and those New Atheists who were not left wing have for the most part realized that Christianity is actually the much lesser of two evils and so have become focused on Intersectionality.