2016 was a combination of 8 years of Democratic control of the White House, hatred of Hillary Clinton for a number of reasons (including sexism), Clinton's ineptness on the campaign trail, over confidence among the average mainline Democratic voter, and a large dose of "I hate all the candidates" (which probably played a role in 2024 as well). There are still a large group of people in this country who will not vote for a woman or a person of color.
Trump is a special circumstance. He played a role on TV that people bought into and many went no deeper than that.