If everyone gets busted all at once (2022-2024 market takedowns is as close to that as it could come IMO) then everyone immediately stops using tor and starts using i2p or freenet or whatever system they may not have broken yet. That's baaahd for business, said the wolf in sheep's clothing.
Although they did run a cp site for months before shutting it down, so they're clearly not opposed to the long-game, especially if it involves national security (it does.)