I just had a look at the guy who is getting 25 boosts in 3 months and I think there are two things at play. The first thing is that he writes widely - and by that I mean he submits to many many different publications some of whom must be nominating his work.

The second thing is that he writes blandly. I don't mean that in a derogatory way. Medium seem to currently eschew anything with a take or that has even the slightest hint of an opinion in it. I know when I write pieces where I'm taking a strong position that they're not going to be boosted (even if I know they've been nominated because the editor has told me).

A more bland piece about how the British electoral system works was boosted before the editor who published it was able to nominate it. Ironically, because I thought it was one of my worst pieces of work - it also happened to be the least contentious and the least opinionated.

Medium is entering a phase of blandification, though the staff-picks allow a certain cherry picking of political positions to be distributed to the masses. More here https://medium.com/lucid-nightmare/lets-have-some-accountability-in-the-staff-picks-please-126224c5aad4