Stalin didn't either, really. His whole spiel was "Communism in One Country", WWII let him take over territory lost in WWI and more stuff to accentuate his power. That communism spread was a mere perk to that, he wasn't actively searching to spread it, it just came with the army.
Agreed both of their views were very different though, Mao was more of a true communist ideal, Stalin a mere dictatorship of his own self. Communist theory didn't play much for him so much as power, and seeing as he had such influence, he could do whatever he wanted and justify it later in terms of socialism...
But yeah, the whole domino effect feared by Eisenhower, Truman, LBJ, everyone, was grossly over-exaggerated and used to justify a lot of wrong doing and errors. Much like today and "terrorism".