Personally, I believe Capers just needed the right parts to fit his D. Maybe he got in his own way sticking with Jones & Hawk last year at ILB, but he didn't have a lot of options. He finally made Matthews an option and look at how that has worked.
Tramon was slowing down, House just couldn't be counted on, and I was a fan of him. Now look at us, with the rookies contributing significantly. Hayward is healthy and playing well. Ha Ha is really coming on in year 2. Hyde is playing like a savy vet. Banjo has developed. Elliott. Palmer. Mulumba. All of these players significant contributors.
Raji, Datone & Perry playing their best ball in years helps. But, Dom has a ton of pieces to work with now. He helped develop all of them.
I'll add, one of the metrics Dom cares most about is scoring D. Yet, we are showing well in a lot of other areas. This is a very solid D he has put together.