A couple I can think of
1. Zero to one talks about the importance of optimism vs pessimism for the future. Compare Obama saying the US needs to get used to sub 2% GDP growth vs Trump saying we can hit 5%. Trump isn't afraid to think big at the very least when it comes to space force and similar big projects
2. Thiel is libertarian and sees Trump as a means to reduce government. Romney got in trouble a few years back for saying a hard truth, that 47% of people don't pay taxes and are never going to vote for less free stuff. At some point it becomes two wolves arguing with a sheep on what's for dinner
3. Personal gain, Thiel has Palantir as well as another company that would use AI to create a "virtual" boarder wall via image recognition