I’m simply seeing the article’s point in asking people to stop following the top, say, 2% most divisive voices.

I would perhaps believe this if the article (or the study) actually listed those accounts. As it is, all they’re doing is leaving it up to readers’ perceptions who the “divisive” accounts are, and insinuating that those are likely misinformation. It’s just pushing people towards the political center.

there were a good number of Bernie backers at Trump rallies

In 2016, 12% of people who voted Sanders in the primary voted for Trump in the general. By the 2020 election, that demo was gone. In 2016 Trump was a rebellion vote against the rigged democratic primary, but after Trump’s first term, they’d all seen what a monster he was, and begrudgingly voted Biden.

I honestly doubt that anyone but moneyed think tanks have much bad to say about him

I don’t think you’ve spoken with many Trumpers if you think they don’t have bad things to say about Sanders. I discussed him extensively with conservatives in my sphere. The conversation usually goes something along the lines of, “yeah, it’s great he’s pro-union and wants to fix healthcare, but he’s also pro illegal immigration and wants to raise taxes through the roof! You know he’s a socialist, right?” The better-informed/ indoctrinated ones will even bring up him (correctly) lauding the literacy gains in Cuba under Castro.