While I can't speak for anyone who voted for him, the basic gist I get from talking with people who did, would indicate that they viewed what the left was selling as a bigger stray from American societal norms. (particularly on some of the social issues)
On a recent episode of The Young Turks (a progressive show), they delved into the topic a bit. They were reporting on these findings
The center-left group Welcome relied on polling of hundreds of thousands of voters over six months for its findings, shared first with Semafor.
www.semafor.com
The group called "Welcome" (and the guy who ran Biden's 2020 campaign) surveyed hundreds of thousands of people over six months (quite a robust sample), and found that the Democratic party messaging and alignment on certain social issues were only gaining traction with one particular demographic, affluent white liberals.
Obviously you can read the report for yourself, but the general summary is, the Democrats have an economic message that resonates, but their alignments on the social issues are putting people off.
Left-leaning economic populism is pretty popular, but not when it's bundled as a package deal with "shout your abortion", the modern form of LGBTQ activism, "Climate justice", and left-wing philosophical viewpoints about the "patriarchy"
Basically what the report highlights is that
- Paid family leave
- Stronger unions
- Expanding Medicaid
- Increasing the minimum wage
....all popular ideas among a plurality of people in the US, but not at the expense of having to go along with the precepts of "abortion rocks!", "drag queen story hour is completely normal", "men suck", "capitalism sucks" (basically, bending a knee to the multi-colored hair college philosophy majors)