Chuck Klosterman's "But What If We're Wrong" is a book that spends a lot of pages trying to answer this question
There's an interesting book you may like. "But what if we're wrong" chuck klosterman an easy to read, often humorous writer.
Chuck Klosterman has a short book, "But What If We're Wrong," predicated on thinking about how future humans will view us. His conclusion is that we're unlikely to know how events will be seen historically until almost everyone alive during the event has passed. We're still yet to know the full effects of the weakening of NATO, the renegotiation of NAFTA, whether leaving the JCPOA with Iran will give them the green light, the rejection of the Paris Agreement, the opening of relations between Israel and several Arab states, and so on.
If I had to make a guess though, Trump will end up better ranked than Buchanan but below Hoover. IMHO, it's difficult to see a pathway to his consideration as a better-than-average President.