Then please explain how the Russians were victorious.
The French executed an assault crossing of the Berezina while building two trestle bridges to get the army out. Tshitshagov failed to stop the crossing and was badly defeated on the west bank of the river.
Wittgenstein failed to defeat Victor who protected the crossing until ordered to withdraw, the last formed units across as he was the rear guard. The French themselves destroyed the bridges after successfully crossing the river.
Kutusov failed to support his colleagues and stayed out of the fight when he was fully capable of supporting Wittgenstein and Tshitshagov. Yermelov stated that Kutusov remarked that it was Tshitshagov's turn to fight the French.
None of the Russian objectives were met at the crossing and the French successfully bridged the river, defeated two Russian armies and accomplished the mission-to get across the Berezina and get out of the trap. Clausewitz remarked on the success of the operation.