It's not the Oline either. He, played, better. It's as simple as that.
The problem is, you are taking a narrow sample of 7-1 record. You are taking a sample of games won. You are disregarding other games. Yourargument boils down to, Tannehill is good when we win. Yes he is, I agree with that.
Yet I would bet fairly heavily that you would never admit a very similarly-worded phrase during that same stretch, "We win when Tannehill is good."
Oh, and that narrow sample size? It's about 67% of the games he played under Gase. The last 2/3.
I'll bet, if you wanted to, you could spin those numbers into "When Tannehill grasped Gase's system, his performance skyrocketed." But you wouldn't want that, would you?