Disclaimer: I know nothing about football, or any other sport for that matter.
Judging only from snippets of news reports overheard, I understand that the manager of a football team (probably better described as head coach) is very important to the success of the team. This is to the extent that if a team performs badly, it is the manager that gets the boot on the grounds that he didn’t pick a good enough team to do the job or train them well enough.
If that is the case, why is it that the same nationality rules don’t apply to the manager and the rest of the coaching staff as they do for the players themselves?