It's important to note that the USSR didn't build into Capitalism, but collapsed into it. The USSR was dissolved from the top-down, not due to structural failures and instability, but due to opportunism.
There was a lot that went into the "murder" of the USSR, and numerous mistakes along the way of its development that were inevitable as history's first Socialist State, but the idea that Capitalism grew out of Socialism is not correct. When I say "supercede," I quite literally mean that Capitalism's mechanisms naturally lead to Socialism over time.