I wonder if part of the problem is that they are maybe water cooling the datacenters full of cryptominers? So not only is there the waste heat from the power plant as originally designed, but also the waste heat of its entire energy output is being dumped into the lake instead of being distributed around town.

I do suspect that this is a surface temperature problem. Lakes form thermal gradients pretty easily so if they are only heating the top layer this power plant could noticeably warm the water even if it is producing nowhere near enough heat to warm the entire lake.

I can't argue against the take that this whole thing is just killing the planet for a profit.