Tallulah, I think that it actually just depends upon the person. Some polymaths dabble in a lot of things. And when I say "dabble" I mean that they simply don't CARE about extrinsic motivators such as praise, accolades, or rankings-- they do those things to get something intrinsic and personally meaningful out of them, and (speaking as a parent to one of this type)-- good luck even convincing them to DOCUMENT such activities well. That's just not the point for those people.

They will dive into an interest for a bit, then completely drop it (maybe for a time, maybe forever) once they've gotten what they need from it.

I think that this is something of a personality quirk, myself. My entire household seems to share it-- so my DH is the one that once he's done with something, he's kind of done with it for good, though sometimes it takes him a while to admit it. Me, I circle back-- but it may be a long latent period. DD is more like me, but she has interests like that which she hasn't touched in a year or more. She'll be back to them, though.

Schrödinger's cat walks into a bar. And doesn't.