Pundits are stupid then. Trump had 48% approval in the exit polls for who voted here and if the voters of Alabama wanted a Republican they would have voted for a Republican. He got outsized turnout from Democratic constituencies, ones he would immediately alienate by doing this.
His best bet is to become some sort of Joe Manchin figure where he builds his own personal brand while remaining a moderate Democrat on most issues.
https://projects.fivethirtyeight.com/congress-trump-score/joe-manchin-iii/
As you can see here Joe Manchin votes FAR less often with Trump than would be expected by his state's lean and yet he's fairly popular there and will probably win re-election. EDIT: And on the big issues that people really care about he has been a uniformly anti-Trump vote.