I know people don't like suggesting that Trump support comes from anything other than racism, and sure racism has to rank pretty low in your concerns, at best, to support Trump, but the weirdos we call "swing voters" are mysterious creatures. Despite the general pretense in The Discourse that these people are making informed decisions, unlike The Ideologues Of Left and Right, their connection to "politics" as people who follow politics understand it is pretty tenuous.
"Life's pretty good, keep that guy in charge" is a motivator, and a reasonable one, for people.
Again you don't have to hand it to him, but no one really doubts that if the economy had been a disaster during his term, his support would have been lower. I don't buy the political scientist "nothing matters but the economy" view, but it certainly matters!