They actually weren't enslaved by the Soviet Union. Yugoslavia essentially liberated itself and Tito chased the Red Army out of Yugoslavia. It's ironic that they're welcoming the Russians now as liberators -- that wasn't how the Yugoslavs ever saw the Russians.
The Communist-led Partisans liberated the country with little help from the Soviets.
It grated on the Yugoslavs that Moscow patronized them and treated them like a colony to be ordered around.
Things didn’t back to normal until after Stalin’s death.