The Clintons have been the subject of conspiracy theories since the 90s at least. So, it's not surprising that this would extend on to Youtube.
(I haven't made an extensive study of this, but my impression is that the American right wing is prone to conspiracies about people or events, whereas the left wing is prone to conspiracies about institutions.)
The article also mentions Trump speeches were more recommended. There's an innocent recommendation: people find Trump more engaging. Of the two candidates, Clinton was far less charismatic - she even admitted she wasn't a natural like Bill Clinton was. So, it's not exactly surprising that Trump was more recommended and more watched.
This isn't to take away from the broader thesis. The recommendation algorithm is certainly worthy of study. And the fact that the algorithm quickly moves from normal to polarizing is disconcerting.
But, it does seem as though the recommendation algorithm to some extent mirrors what we see in talk radio and other media segments in America.