Instead of mining Bitcoins directly, couldn't one of these huge processing farms dedicate their processing power to instead discovering the private keys of the largest wallets on the ledger?
I realize randomly guessing private keys is unlikely. However unlikely though, it would seem you'd increase your likelihood for each additional guess and a mining farm could do a lot of guessing with 24 hours a day 365 days a year. And, any particular guess could be the lucky one that cracks the wallet.
I'm asking this question not because I want to do this. I'm asking it because "if I can think of it" someone else is probably already trying it.
Each day, this farm could query the top 10 wallets in the ledger and just do random private key guesses all day long. If these big accounts switched wallets each day, it wouldn't matter, a farm would be guessing on those new wallets constantly (what ever is top 10, at any given time, could be constantly randomly guessed at).
What prevents this?