Both, but Mike McDanold's schemes have been proven to work. They worked in Baltimore, which is why het got the HC job. Eberflus as the Seattle DC, and they're probably a middle of the pack defense.
McDonald knows how to scheme up blitzes that free up players that can penetrate the backfield...and knows how to disguise these blitzes pre-snap. Once a QB doesn't know where a blitz is coming from pre-snap, now you're in that QB's head. And then, at the snap, many QBs stat looking down at the front 7 to try to identify the blitz before looking downfield to read the coverage.
And oftentimes, in the 2nd half, the QB's clock is sped up...they feel they have to rush on every passing play.
For a 2nd-year QB, you just can't prepare for that...it takes experience. And even veteran QBs fall victim to such schemes.
But yes, ultimately, Seattle can stop the run with a solid front 7, which then sets up 2nd and 3rd and long. But McDonald's blitzes a lot on first down too, guessing the run play direction. He's REALLY smart, and his defenses are well coached...no matter the players.
Hec, not many football fans could name more than 1 or 2 people on Seattle's defense....not a lot of known studs, just a lot of solid, well-coached players.
So McDonald deserves A LOT of credit....to win a Superbowl in your second season as a head coach, with a new QB, it's impressive. And he's young. Sky's the limit.