The right way to think about it is to realize that hiring is a very difficult business, and we all make mistakes. So it's not who they hire, but who they intend to hire. They still miss.

So A players end up hiring B players when they don't want to, and sometimes A players sneak through the B player's filter.

And this is why, when people that are apparently very good leave your company, you have to wonder if you have to much B team, and you are letting them run amok.