The main change is Marshal Yanda going from +12 to +45 in one year (Run blocking from +9.5 to +35.1, Pass blocking +4.8 to +10.1). Is that because of Kubiak? Probably, but it's also possible that Yanda is hitting his prime as well. Also, dumping -17 Micheal Oher helped a ton, as well as promoting Osemele to full time status going from -4.2 to +21.7 and Wagner going from +0.9 to +12.5. Oh, and demoting Gradkowski with Zuttah at center where Zuttah performed replacement level (+1.5).
Then again, how did Eugene Monroe regress from +20.5 to -12.9? Or why is newcomer James Hurst -24.5 under Kubiak?
Not everyone improved under Kubiak, but it seems a combination of blossoming talent and a new coach helped turn that offensive line around. So big picture I think Kubiak does deserve credit for that OLine's success after such a dismal previous year.