Looking at a map of post-WWII Austria, I realized that the Soviets occupied much eastern Austria, including eastern Vienna. So why didn't they form a communist puppet state like with East Germany and North Korea?

I understand that the Allies organized elections in which the Communist Party of Austria was defeated, but why would the Soviets care? They didn't let East Germany have elections; they just declared that it was a separate state.

Why did the Soviets eventually agree to give up their occupation zone to a democratic Austria? The Wikipedia article explains that the Soviets eventually let it go in 1955, it just doesn't go into any significant detail as to why.