The fundamental problem with Trump is not his ideology. I'd much rather have a conservative president myself.
The problem is that he expects fellow Republicans to put loyalty to him above loyalty to the Constitution and their oath of office. We've seen this over and over now.
Governor Ducey of Arizona was on very good terms with Trump right up until the 2020 election. Trump became angry and publicly lashed out at Ducey for certifying the results even after Ducey pointed out that this was a formality required by the state constitution and his oath of office and that he had no choice in this.
We saw a very similar situation with Mike Pence. Constitutional scholars were unanimous that the Vice President simply presides over the session and does not have the authority to change its outcome. Trump still appears to be angry with Pence for not attempting to overturn the election by executive fiat.
The recent attacks on William Barr and Mitch McConnell fall into the same pattern. Trump puts his own ego on such a high plane that disagreement is perceived as disloyalty. As a candidate in 2017, he promised to have the "best and most serious people" in his administration. As President, he repeatedly railed about the ineptitude of his own hand-picked choices.