My suspicion is that a few users have a ridiculous amount of bitcoin across many many wallets and that they use these wallets to prob up the value of bitcoin. This slowly drains their bitcoin assets, but keeping the value of BTC high relative to hard currencies like US dollars means that they still make lots of money. There's enough wealth concentrated in enough individuals that they could probably go for years propping up the value of bitcoin until they run out of enough bitcoin to keep the value propped up or until BTC actually becomes useful as a reserve currency for the real world. If the latter happens first, then they get rich from making something useful. If the former happens first, everything comes crashing down like a house of cards, but they still get rich.
