France falling so quickly, turned out to be a blessing in disguise. Stalin still needed a few more years, most say until 1943, before he would have had the capability to launch an offensive war. By then he was hoping the French, German and British armies were so depleted, so as to enable the Red Army to swoop all the way across Europe. So at least by having France fall, and saving the German and British Armies for the most part, it allowed Hitler to attack Russia, and the Allies to at least win half of Europe and keep it out of the hands of Stalin.
I almost said that if you wanted to thank anyone for Soviet domination of Eastern Europe, you can thank the French for surrendering to the Germans. On the other hand, it’s reasonably certain if Germany and the Allies had a Western Front stalemate into 1942, he would have felt strong enough to blackmail Hitler. His plan was to have the Red Army expanded, equipped, supplied and led by mid-1942. It might have been better led, but would still have had too many Pavlovs and not enough Rokossovskys.
In 1941, the Red Army was not ready for war and Stalin knew it. But he’d gambled on his Non-Aggression Pact and lost.