In fairness, before the Molotov-Ribbentrop pact, the USSR were trying to form alliances with the western allies throughout the 1930s. Maxim Litvinov worked hard to form an alliance with the UK and France, but both governments were more concerned with suppressing communism, and in France’s case, directing Nazi Germany eastwards suited them better.

The ideal outcome for the UK/France was for Nazi Germany and the USSR fight each other to a standstill, which would weaken both Fascism and Communism.

The Molotov-Ribbentrop pact was made by necessity for the USSR and convenience by the Germans. It is no more an endorsement of Nazism than the Munich Agreement was.

The Russian military was never strong enough to face the full focus of German advancement, and in 1938/39 they were in no position to take them on.