This can be quite frustrating if you want to figure out “what happens if I do X”, and all the answers provided by science turn out to be about “what happens if people kinda want to do X, but then most of them don’t”.
I mean, it is good and potentially important to know that most people who kinda want to do X will fail to actually do it… but it doesn’t answer the original question.
Occam’s razor says that Trump makes populist statements that appeal to the kind of person who votes for Trump. Whether those are actually good ideas is irrelevant. Mercantilism sounds good to a person who doesn’t know much about economy. Territorial expansion rhymes with “make great”.
21st-century economics is just as irrelevant as e.g. 21-st century medicine. Scientists are not an important group of voters.