If you had any incentive to find out, and weren't so lazy, you could have done a simple search to find out, so here's the historical aspect of what the annual victory parade is all about: The Soviet victory over Nazi Germany in 1945. Despite being a communist republic at the time, the Soviet Union's joining the allies in defeating Hitler was extremely important at that time. And they agreed to enter the war against Japan once Germany was defeated. It would have happened had we not dropped the bombs. Russians have every right to celebrate their victory against fascism, like we have the right to celebrate the 4th of July every year, at least until the fascist RATS cancel it.
I celebrate the people who fought for their motherland against an evil invader, but not their leaders.
Then you think the Russian Federation and the USSR are the same thing? So do I.