Why the incompetents will get more opportunities to promote in a company?

The competition from the market will not crash the company, but the bad behaviors of staff are the biggest threats to company. The essence of management is to prevent the inside threats. And the biggest threats are come from the quite capable staff. That is why the boss usually doesn’t provide more rights to the best staff to performance, and will strict their activities. And boss believes the incompetents can’t do worse than now.