I don't think it's specifically "Salah-bashing". When he was here, he was dog-sh*t bad. He went elsewhere, and appears to have got better. It happens.
It's the same old 20/20 hindsight that is hugely prevalent in here (and in lots of other areas of society, not just football) that bitchbabies use to moan about De Bruyne, Lukaku etc being sold, when all they did while here was take up a squad place and fail to impress whenever they played (OK, OK, I know KdB had a decent 20 minutes against Hull or some such northern pub team).
Salah was pants, got a bit older, got a bit more experience, moved to a team where they play in a very specific way that appears to be absolutely perfect for his Jack Russell-like chasing after a ball, so looks like a footballer rather than a sprinter. SWP was 'kin excellent at that, and we let him go as well. Even Gronkjaer scored.