He is classically selfish. Believes he is the center of the world. He can play by his own rules. Very angry with obstacles. Will seek revenge against anyone who offended him.
Behind the scenes there was some discussion about invoking the 25th amendment including among cabinet ministers. I suspect the reason it didn't progress was fear. Trump had a strong voter base that supported his vindictive responses to any criticism. His base supported him much more than the Republican party.
Another example of Trump's power comes with Kevin McCarthy. After January 6th he used some harsh criticism of Trump, but shortly afterwards he met with Trump and re affirmed his loyalty. It was quite a tough road to reach his goal of becoming House Speaker, but would not have been possible without Trump's support.
Loyalty is a key requirement His power comes from disgruntled voters who think they have found their champion. They feel their lot in life has been affected by government rules and admire Trump's belligerent style.
After the 2020 defeat some were fired and of course a few resigned. The January 6th Inquiry was totally Republicans who knew Trump well, but his base paid almost no attention. They for the most part dismissed the testimony or felt his championing their interests more than made up for it.
The day before his 72nd birthday he was charged with illegally taking possession of classified material. We were shown what sloppy conditions the material was stored and heard stories that he sometimes presented some of the material to guests with little regard for security. His base thought it was more proof of persecution.
Trump sued many of his enemies and also needed cash for his own legal problems. The money came from his campaign funds. His base presumably felt this was necessary to protect Trump's power.
Another factor confirmed in this account was that he hated any criticism of Vladimir Putin, a man he admired for being a strong man. This meant also that he promised to stop any any support for Ukraine. The Republicans had had policies attacking Soviet and Russian aggression. That is reflected in current Republicans opposing aid to Ukraine.
As an outsider it seems incredible that Trump has so much support. It will take more than evidence referred to in this book to change his base. One can hope that the insanity will at least gradually erode with all the legislation scheduled. Unfortunately his tactics of delaying help his cause.