The USSR's leadership under Stalin and co. was too far gone to spread revolution internationally before WW2. When the capital-C Communists pivoted from their "succdems are social fascists" position to popular frontism, they ended up playing a counterrevolutionary role within and close to the imperial core, a policy meant to defend the Soviet bloc geopolitically, the logical extreme of "socialism in one country" as a long-term strategy rather than as a tactic. The 3rd international's intervention in the Spanish civil war was just about the final straw that prompted the formation of the 4th international to begin with.
The USSR's leadership under Stalin and co. was too far gone to spread revolution internationally before WW2. When the capital-C Communists pivoted from their "succdems are social fascists" position to popular frontism, they ended up playing a counterrevolutionary role within and close to the imperial core, a policy meant to defend the Soviet bloc geopolitically, the logical extreme of "socialism in one country" as a long-term strategy rather than as a tactic. The 3rd international's intervention in the Spanish civil war was just about the final straw that prompted the formation of the 4th international to begin with.