Among other factors, I think humans have a certain instinctive drive: when there’s a broad sense of social malaise—when lots of people feel there’s something wrong with their social institutions, but there’s no consensus on how to remedy it—they gravitate toward whatever thing the social establishment seems most afraid of, because in our deep history that’s been an effective way to break out of dangerous institutional stasis.
Depending on the social establishment at the time, that anti-establishment movement could take many forms—religious, ideological, nationalistic, etc. So I think Trumpism is an inevitable reaction to the rise of the neoliberal establishment under Clinton and the Bushes: the underlying cause of the neoliberal malaise is economic, but the most visible social anxieties are over racism, sexism, and other social factors. So that creates a feedback loop of growing fear that attracts those feeling a general sense of discontent.