how someone you're following will be thinking a lot about something/happen to come across several good chosts in a row about something/go down a rabbit hole on something/be hyperfixated on something/otherwise in possession of a lot of interesting chosts on a topic, and they'll rechost several in a row (and maybe have an original in there too), and so you're left with this dense burst of topic-focused information to chew on.
Maybe it's something that you think about a lot. Maybe it's something you never thought about at all! Either way, now you've been given a cool opportunity to learn a lot, quickly, and there's gonna be people hanging around those comment threads who are also into this thing and knowledgable.
And on a side note, if we had an algorithm curating our feeds, that property would just... Not be a thing. That wasn't the point of me writing this at all, but I think that's a relevant observation.