Because actions like this are less about Russia winning and more about Ukraine losing.
They did this to cause decades of damage to Ukraines industry and an ecocide.
It’s the same reason they fire missiles into civilian buildings, destroy power plants during winter, rape and torture children, execute teenagers and fire on civilians. L The terror and damage destruction is the point.
Destruction of this dam was also a war crime by Russia.
They gain a lot by trying to cover up another of there war crimes and to muddy the water with their firehose of falsehood propaganda method.