This claim makes zero sense. The Russians had already withdrawn their army so the opportunity to trap them was nil. Not only that but any future opportunity to trap them was also lost. Meanwhile the Russians got a free moat at a crucial moment when they were retreating and the Ukrainian counter offence was stopped in its tracks.

In WWII the Russians blew up a damn on the same river (killing tens of thousands of their own civilians) to stop the Germans advancing. It’s the most Russian tactic ever. This is exactly how they fight.

Yes we don't know who controlled the dam and would be able to place required amount of explosives in the location they were detonated at. It's shrouded in mystery.

There's no "their side" here, both sides of the Dnipro are Ukrainian territory; one of them is temporarily occupied.