I've been here since the API exodus in 2023 and have seen it enough times to know that it's typically someone coming in new from reddit, seeing that the feed of new stuff here has an endpoint and recharges slower, so they want to make a repost bot so there's more content. They'll never actually read that content, but they just want it so they have something to mindlessly scroll past. I don't think they're going for popularity contest, at least not primarily, anyway.

Giving them the benefit of doubt, I think they're just highly misguided.

I could totally be wrong. This is just based on my observations and the occasional post in c/Fediverse when some new user talks about how it feels inactive here and suggests reposting crap from Reddit. I also try to go with the most charitable explanation for behavior I see.