I wouldn't say they are widely known for hating the electric grid but hey here we are: https://en.wikipedia.org/wiki/2026_arson_attack_on_the_Berli...

Climate activists are definitely known for disliking fossil fuel plants - and there's one directly next to that.

I could see an activist naïvely thinking that this would sever that one power plant from the grid, making a clear anti-fossil statement. Still a bit of an odd choice (it's gas-powered, Germany has far dirtier lignite-powered ones), but not unthinkable.