Yeah, I suspect a few factors are at play. Mastodon has become big enough (particularly among more serious/nerdy people) to be noticed so that makes it a target for paid influencer type trolls. Also Mastodon is bigger among nerds, troll farms will be paying attention to this. In some places, like Canada, the fediverse is pretty much the only social media that actually provides a social media space to post or talk about news these days (with Meta blocking all news links and Twitter being X and all). Also, more people are just opting out of social media all together. Also, Twitter is less fun for individual trolls these days because there's less of an audience, individual trolls are people who are desperate for attention and engagement, any attention or engagement at all.