What helped them is putting the right people in charge of Zen design and intel fumbling 10nm due to their own hubris.
AMD was fine with having GloFo as a fab until 20nm process. They were already behind, but not terribly.
AMD even used TSMC for their CPUs and GPUs before Zen. Ontario was fabbed at TSMC in 2011.
Point is AMD as free to shop around. Only in 2016 the agreement was amended that GloFo would be preferred for 14nm and 7nm, but since they decided not to work on 7nm, it freed up AMD.
Zen 2 is also where Ryzen went from "exciting and competitive, but not top of the line" to actually giving Intel a run for their money in more than just highly multithreaded workloads.
Improved architecture put AMD within striking distance of Intel and the move to TSMC allowed them to pull ahead.
AMD used TSMC for their CPUs (not IO die!) at least for one generation, and TSMC actually dropped the ball that time and AMD went back to GloFo.
Once again, AMD was fabless since 2009 it's a fact, and it's also a fact that it didn't help them at all.