Title states all. It can be multiple reasons or just a few. I've twiddled to down mainly to 3 reasons, "roughly" that is.
The Stalin personality cult that would subjugate various Soviet leaders to being wild conspiracy theorists and untrustworthy of themselves, their inner groups, intelligence, other leaders of the USSR, etc.
The inability for the Soviet Union to give more independence or political freedom to it's satellite states, and freaking the fuck out when states weren't following the strict set of guidelines from Moscow, (also party leadership changing the internal politics and Moscow relationship of it's satellite states every time a Soviet Leader died/changed their mind on how to operate it's states, Belarus comes to mind.)
Finally, the economy, and the Soviets too fraught with conspiracy to adopt to the global economy when the world started to surpass them on many economic fronts, along with a bloated military budget.
These are my reasons, I akin this degradation like a large column of marble representing USSR and the issues that toiled the USSR like many hammers and chisels, some are bigger than others but ultimately no one hammer or chisel brought an end to the first great socialist experiment. Thoughts?
-7DeadlyFetishes
Belarus wasn't a satellite state tho? It was a part of the USSR. What exactly do you have in mind here?
Seeing as the various different "satellite states" had various different policies, i.e. the more liberal Polish and Hungarian forms of economic policy when compared to the GDR or the split in the foreign policy of Romania when refusing to invade Czechoslovakia in '68, or not supporting Ethiopia when Somalia invaded, I think it's unwise to paint the Soviet bloc as the USSR and a bunch of puppet regimes. Those countries each had their own policies set by their own parties, admittedly with heavy influence from the Soviets. How much more "independence or political freedom" would you have asked for?