Trotsky leader of the USSR

That, and although he disliked Stalin, contrary to what Trots want you to believe, he didn't want Trotsky in, although he liked Trotsky more, he preferred Stalin to succeed him.

Oh, but wait, it's Trotskyism, let's just yell Stalin's evil, and therefore our ideology's right, right? yeah, totally, it's not like Trotsky only joined the Bolsheviks because they had more support, or anything.

I think without Stalin and his purge the USSR would have lost or have come much closer to defeat than it did in our timeline. Also trying to spread communism to other countries by using Soviet soldiers immediately after the civil war seems like a very bad idea.

It would have killed more people than Stalin ever could have dreamed of.

If there's one thing Trotsky got right, it's that the Revolution had to be spread for it to grow. Communism never really grew as a power until the mid/late-1940s because Stalin never aggressively expanded it until then. Then it could attempt at world supremacy. Yes, people would die. But it's not like the early 1900s were peaceful without an aggressive expansion of Communism.

Though Trotsky probably wouldn't have been able to run the USSR for shit.

Well, if Trotsky came to power things would have been different. For one Trotsky would have been more interested in spreading the revolution than actually bringing up the Soviet Union. He would have left the agricultural system, for the most part, intact and production and industrialization would have slowed. He would given support to communist rebellions and parties in other countries especially in Post-WWI war-torn Europe and during the depression. Who knows? It could have been possible that he would have help the German Communist party take power and prevent WWII. But Trotsky would probably eventually cause a world war in order to spread communism. As for life in the Soviet Union, Trotsky was against the extreme bureaucracy that was being established by Lenin, Soviet Society would have probably been a more open society and people would have more rights and freedoms than under Stalin. However I think Trotsky would have betrayed his own ideals of a "dictatorship of the proletariat" and established an Authoritarian government to have more control and prevent rebellions.

You do know that Stalin put Thälmann back in charge after being fired from the KPD in the first place, right?

Plus the fact that Thälmann and many of his followers were Stalinist, i don't see Trotsky helping them.