There are 210 people in the league, and each one must have had a certain rep/time on Steem to qualify.
I admit, the level of engagement isn't what it used to be, but that can be said across the platform at present I think.
One thing worth mentioning is that 50% of the post rewards are used as prizes for the top 20 at the end of the season. I take 30% as author, and @acidyo takes 20% for organising the contest.