I think the hope is that the lack of water for cooling will cause permanent damage by overheating. But the reality is there are failsafes to prevent this.

Shutting down a data center for the cost of a bag of cement is a good cost to loss ratio though. It may only be for a day but that is easily repeatable. Shut it down every few days while they are already losing money running at a loss and trying to show some sort of usage stats that will get fucked by the repeated shutdowns.

Obviously you have to find multiple ways to fuck with them like bad additives in their diesel generator fuel tanks. Drones dropping epoxy into the cooling fans on the roof.

They don't just blindly use whatever water comes from the lake and put it directly into the loop.

They'll have treatment, filtration, and cossosion-resistant parts, and probably separated loops where the only liquid that directly interacts with anything important is completely isolated from the intake and outflow water.