the fees are limited by the market cap of bitcoin. at any given moment there is a finite amount of fiat even if it is continuously increasing. bitcoin's price tends to track, eventually, the increase in the supply of fiat, thus it is a hedge against money printing, and a store of value.

any attack they mount has a limited lifespan that only holds until the next adjustment that brings bitcoin's price to or above the corresponding change in fiat supply. at that point, their attack becomes uneconomic, and they stop.

that's the reason why it's not nonstop.

if they focused on keeping it high they would inevitably also raise the price of bitcoin, and that then counters their continuance. The more they try, the worse they make it for themselves, and everyone who isn't transfering their bitcoin around is grinning.