Yes, it being free on PS Plus is literally in my post you replied. It's a combination of those things and Part 2 having mediocre legs if you compare it to other high profile PS exclusives on gamstat. You just can't spin that. I hope the legs will pick up somehow, I loved the game.
There is only 2 titles above TLOU2 in the same time frame, is Spider Man and God of War.
And no, TLOU2 doesnt have mediocre legs.
The only high profile game first party Sony game to get mediocre legs is Death Strading.