You assume those voters believe Jan 6 was an insurrection. Many of them don’t. Whether thats a fault of the media/bubble they’re in or gross naivety/negligence is a different discussion.

If you go with the presumption Jan 6 was a mob that got out of hand (not my position, just one of the perspectives), then the idea that he wasn’t able to enact his agenda due to the opposing party, coupled with the shenanigans of the other option (no democrat primary for Kamala being one, with democrat party having done similar in the past with Bernie), then claims that the democrats are spinning Jan 6 and risking another term with him seem more reasonable.

Whether I or you agree with those premise is separate from what the zeitgeist is for much of America

I simply don't believe that any substantial number of voters think January 6 wasn't an insurrection. Trump openly spoke for a full month beforehand about how he was going to overturn the election, and continues to this day to insist that he should have been allowed to. People who claim it was a protest that got out of hand are not confused, naive, or in a media bubble; they're just lying.