Actually, Stalin repeatidly attacked Trotsky for supporting World Communism in the years following Lenin's death. Stalin believed that 'the victory of socialism is possible first in several or even in one capitalist country alone.'
You completely misunderstand what was being said. Stalin was (correctly) explaining that World Revolution was not possible AT THAT TIME. He never abandoned the cause, but the early attempts at fostering revolution (i.e. the attempted revolution in Germany that Trotsky had supported and Stalin at initially voiced his opposition to) were doomed to fail. The thing that Trotsky and his revisionism seems to be willfully ignoring is that Stalin was correct. Not only were other nations not ready to go Communist, the Soviets were no position to offer much support. On top that the initial attempts had made the SU an international pariah and was constricting its access to loans and resource that it desperately needed. It was Stalin's backing off of that nonsense that eventually made Britian and France restart loans and industrial assistance trade deals.
The fact is that Trotsky intentionally misrepresented Stalin's pragmatic argument.