He didn't put all his eggs in one fragile basket. He brought in Matt Flynn, also the guy from the chargers, who was supposed to be the starter, and drafted Wilson. You can say 'he got lucky' but it's a case of luck = the intersection of preparation and opportunity.
His defenses have also been better than the Rams, his running game - better than the Rams, even his so-so wide receivers and passing game - better than the Rams. So, yeah, except for the division titles, super bowl appearances, lombardi trophy - he's been just like Fisher - they both worked at USC at some point in their careers.