Are Governments Comprised of Angels?

So, comrades:

If you were to get what you wanted, an abolition of capitalism and a State where the workers owned the means of production, what happens next?

My basic assumption is that these workers would form a type of government that would decide how capital and labor was employed.

What has always baffled me is this: Why on Earth do you think any government assembled with the egalitarian goals of Communism would not find itself rife with corruption, cronyism, and mismanagement?