And if they do know how to run them, they will simply become the new bourgeoisie, being all arrogant in thinking they "know how to run things" or that the machines and the business "won't run without them," or even having the audacity to ask for higher pay, just because they think their jobs are "more important" or "more difficult."
This can happen if elite don't have pressure from the population and expect to stay in the power forever. Late USSR is good example.
However, planned economy with democracy and elections won't let above problem to happen.