Who voted for Donald Trump? Why?

I think it's best to focus on demographics (which provide number-estimates) vs hand-waving themes. (Urban Archipelago, Clinger Party)

2016 (vs Hillary Clinton)

He got 57% of the electoral college votes, but 49% of the popular vote

Trump's crucial victories in the Midwest were aided in large part by his strong margins among non-college whites—while Obama lost those voters by a margin of 10 points in 2012, Clinton lost this group by 20 percent. The election also represented the first time that Republicans performed better among lower-income whites than among affluent white voters.[496] Clinton however had the majority amongst lower-income Americans overall. Trump got 81% of White evangelical or born-again Christian. Trump got 61% of white 45-and-older, and 67% of "White no college degree" (both sexes). For income above $50k it was pretty close (below-$50k was solid Clinton). Trump got only 49% of suburbs, but 62% of rural.

• remember, all those are the breakdown in popular vote.

2020 (vs Joe Biden)

43% of electoral votes, 48% of popular vote

Voter demographic data for 2020 were collected by Edison Research for the National Election Pool, a consortium of ABC News, CBS News, MSNBC, CNN, Fox News, and the Associated Press. The voter survey is based on exit polls completed by 15,590 voters in person as well as by phone... The Brookings Institution released a report entitled "Exit polls show both familiar and new voting blocs sealed Biden's win" on November 12, 2020. In it, author William H. Frey attributes Obama's 2008 win to young people, people of color, and the college-educated. Frey contends Trump won in 2016 thanks to older White without college degrees.[360] Frey says the same coalitions largely held in 2008 and 2016, although in key battleground states Biden increased his vote among some of the 2016 Trump groups, particularly among White and older Americans.[360] Trump won the white vote in 2016 by 20% but in 2020 by only 16%. The Democratic Party won black voters by 75%, the lowest margin since 1980. Democrats won the Latino vote by 32%, which is the smallest margin since 2004, and they won the Asian American vote by 27%, the lowest figure since 2008.[360] Biden reduced the Republican margin of white men without college educations from 48% to 42%, and the Democrats made a slight improvement of 2% among white, college-educated women. People age 18 to 29 registered a rise in Democratic support between 2016 and 2020, with the Democratic margin of victory among that demographic increasing from 19% to 24%.

• Within the white/non-college group, I see huge Trump support among (a) protestants, (b) people who say climate change is not a serious problem, and (c) people who think the economy is the "Most important issue to your vote". (It's interesting that the poll didn't offer climate change among the top 5 "Most important issue to your vote" items (which were: the economy; racial inequality; coronavirus; crime; healthcare policy).

A problem with polls on beliefs is that there could be a lot of back-justification (decision rationalizing) based on your candidate choice - e.g. if you're a Trump supporter (for whatever reason), you might back-fit a justification for that (which you're willing to answer in a poll), so in 2020 you say "the economy is the most important factor" and "the economy is doing great".