> Hiring managers are DESPERATE For people
You already admit to this. Now add to this the pressure on hiring managers to fire a certain number from his team. The only course of action he can take is to convince the bar raiser to accept the new hire even if the candidate is subpar.
It's strange that even after 500 interviews you have not this. I've been involved in less than a fifth of that interview number, and already seen this.
Even if you have not seen such cases you don't have any basis to claim that it doesn't happen. Logic and majority of evidence indicates that this takes place.