I don't have a major issue with any of Trump's Supreme Court pics. Amy Coney Barrett is probably the best selection he made. Nepotism doesn't make a difference when the votes come in.
The votes came in, he was a sore loser as you would expect a petulant, narcissistic man-child to be. He left office when he was supposed to and Biden moved into the presidency.
If he wins again, which is looking more and more likely, he will also leave office when he is supposed to. He's not a dictator. He's not a king. If he absolutely lost his mind and decided he was going to refuse to leave, he would be removed by force.