Trust me, nobody dragged Saban kicking and screaming anywhere he didn't want to go. Saban is one of the smartest coaches in the game and isn't afraid to evolve with the times. Kiffin did exactly what Saban hired him to do, at least on the field. But that offense was going to evolve with or without Kiffin.
I still fail to see need why Saban would need to 'evolve'. All that talk started around 2013, when honestly was still the best team in the country, beaten on a fluke kick return. Does anybody really think Alabama wouldn't have beaten Jameis Winston in the BCS title? Auburn should have beaten them, they were up 21-0.
Then he hires Kiffin, and they aren't as good in 2014. That's because they lost McCarron. 2015, worst offense of the Saban era, but still win the title. 2016, they move to Hurts, Kiffin gets chewed out and leaves, they barely lose the national title on about as equal of a game as you can play. Same 'evolved' offense finally gets stymied against Georgia in 2017, but then Tua comes in and wins the game. Next year in 2018 to now they set the world on fire with Tua and a set of about 4-5 NFL caliber receivers.
Looks to me like it's more about the players they recruited, than some evolution of offense. And it's not until now that Alabama's defense has regressed, but some of that is a product of the offense scoring more and being on the field.