They thought he would quit back in 2017
A lot of Congressional Republicans thought so too
They though he was just like them and would fold at the first bit of negative press
The Lunatic left has thrown everything at him they have in their playbook, and have failed every time
He WON’T back down
Nobody who talks about using the 25th amendment seems to have taken the trouble to read it. (It's not that long...the relevant section is less than 300 words long...even a Never Trumper should be able to read it in less than an hour.) If a President was declared unable to carry out his duties, the Vice President would become Acting President, but the President would not be removed from office. He would still be the President.