People we're talking about sending missionaries into the church in the late 90s for this reason, people railed against this rise of the influence of para-church organizations and multi-denominational initiatives.
But the people who wanted to keep the definition of the american church a "small c" lost pretty thoroughly to the political action clubs.
The SBC boycotts/cancelation of Disney in 1997 and the memetic cancelation of General Mills cereal was all outworkings from Jerry Falwells take over of american christian expression using Francis Schaeffers films to provide emotional impact and introduce new political reasoning and adopt what was previously "the roman catholic" issue of abortion as a primary political, religious and social wedge issue. That was the core "ratchet" issue.
With Lamar Alexander, Alan Keyes and a few others politicians campaigning with extremely heavy religious strategies in republican primaries in 96 you see a turning point and culmination of the political work of Falwell and others through the 80s. It showed that there was effectively no pushback left among evangelicals to messaging that conflated Republican & Christian, the assimilation was sufficiently complete.
Idk, there's almost an infinite amount of causes and drivers but there were a lot of bad turning points along the way.
In what feels like a past life I actually went to a influential seminary in the early 00s, the few older professors we're academic and rigorous, the rest of the younger professors and the students themselves we're... bad, just really awful people with odd pathological relationships and furtive self serving behaviors, the amount of extremely insular "christian celebrity" worship was shocking to me at that age.