[eropple]

How many of them 1) always published long-form material, and 2) hit their stride/"were selected by the algorithm" in the last few years?

I would believe that what you describe is true for long-established YouTube personalities, and I can think of plenty myself, but I can think of pretty few that haven't been doing it for at least five years or so (with the exception of the woodworking space, where it seems like perhaps there's still some growth opportunities despite plenty of creators--my guess is it's because the ad revenue is way better there). I follow a lot of smaller essayists 'cause I like that sort of thing and have a friendly recommendation network to leverage; YouTube very rarely recommends me long-form content, in either Search or Suggested Videos, from somebody I've never seen before.