Struggle to understand the logic in that he was garbage for us, in our league, in the environment, maybe didn't fit in with the other players. Who knows. But it 100% didn't work out. He can score 30 goals for PSG, all it proves is that he's more suited elsewhere.
We don't know him personally but I think hand on heart if anyone asked him whether he was ever happy here, the answer would probably be an emphatic no. He's probably just happier living in Paris with a few more mates around and he'll probably play better as a result.