Ehh, I'm currently in the camp that says that this is not 100% planned. Rather, the seemingly intended plan was a significantly smaller breach that would flood Ukrainian positions downriver and stop the minor skirmishes with Ukraine and claimed buildup. That is pretty much what they were initially congratulating themselves on doing, after all. By the sound of it, it was only later that they realized that they had utterly screwed up and started blaming Ukraine, shelling the remnants of the dam to try to fabricate evidence, and the like. It's a bit more parsimonious to assume that the specifically relevant incompetence was in the handling of a planned dam breach than something more large scale. Either way, Russia's not likely to investigate. Apparently, about a week ago, instructions were made that military related dam damage in Ukraine is not allowed to be investigated until 2028.
The targeting of humanitarian efforts is pretty much SOP for Russia, either way, and doesn't require any special plan to explain.
If anything, that would speak to Russia's inability to locate the offensive in time and mount a meaningful defense than anything else.
Either way, Ukraine seems to have breached at least some Russian defense lines north of Melitopol and Tokmak, in addition to gaining high ground to the east of there.