The best part of the fediverse is that anyone can run their own server. The downside of this is that anyone can easily create hordes of fake accounts, as I will now demonstrate.
Fighting fake accounts is hard and most implementations do not currently have an effective way of filtering out fake accounts. I’m sure that the developers will step in if this becomes a bigger problem. Until then, remember that votes are just a number.
I think it would actually be pretty easy to detect because the bots would vote very similarly to each other (otherwise what’s the point), which means it would look very different from the distribution of votes coming from an organic user base