I've said before, I think Yan has insane fight IQ and makes some of the best adjustments mid fight of just about any fighter we've seen. Given that they've fought previously, it's no surprise that Yan would have made the necessary adjustments to put on that masterclass performance
However I definitely think Merabs over activity is a factor. We saw it with Lawler against Woodley. Tyron was never a championship caliber fighter imo, but he sat out for a year and a half while Lawler went back-to-back-to-back in grueling FotY wars against Hendricks, Rory, and Condit. After being worn down like that, Woodley was able to capitalize and secure the belt. I dont think that's the biggest factor with Yan/Merab, but it's certainly worth considering