It makes 100% sense for Russia to do it. 1. Russia is on the defensive preparing for the Ukrainian counterattack with their new Western Weapons, blowing that dam eliminates crossing that river as an attack vector. 2. Now Russia can redeploy forces that were stationed along the river to the Zaporhizia, Donbas, or Savotva areas (which they are currently doing, might I add). 3. It’s a scorched Earth tactic that is devastating for Ukraine. Now Ukraine is busy rescuing civilians and the environmental disaster, rather than focusing on their counter offensive. 4. Russia has done this before, specifically in WW2 when the Nazi’s were approaching Moscow.