There are ample reasons to believe that Trump is losing his cognitive functioning. He has repeatedly confused Biden and Obama, and confused Haley and Nancy Pelosi. He mentioned Haley's name five times as being in charge of security on 1/6/21, when he obviously meant Pelosi. He is slurring his words, and his speeches aare becoming more and more confused and rambling. In light of all the legal pressures he is feeling, there is every reason to believe he will self-destruct within the next few months, and it would be silly for the GOP not to have another candidate still in the picture when that happens.
Some Democrats would prefer to run against Trump, since the chances of winning are so much higher (Haley beats Biden by double digits). But the down side of a Trump victory vs. Biden is just too great. as it would mean the end of our 248-year old democracy. And a Trump victory is quite likely. Trump has an easy lane to victory; he can simply brand Biden as a warmopnger, and boast about how there were no wars on his watch, and now three (counting vs. Iran) under Biden. Biden's speeches are now regularly interrupted by protestors protesting U.S. support of the genocide in the Gaza Strip, and this is only going to get worse. By the time the Trump machine gets done with him, he will be forever known as "genocide Joe".