Scale is a large factor in how well these funds can perform. Even Buffet famously talks about how difficult it is to allocate order-of-magnitude larger amounts of money, because the opportunities are harder to find and you affect the market more as you increase your buying.

There's a good amount of funds who actively keep their AUM low. If they have too much money in their strategy, it will discovered and that kills the golden goose. Or, there's just not enough liquidity in the instruments traded and the money would just be idle. Lots of high alpha funds have forced redemption just for these reasons alone.