I think he's he's obviously very good, but he's also insanely lucky.
I don't know if he's got that aura that scares defenders, but I mean watford gave him 0 respect. They left him insolated 1v1 with a slow CB, then he proceeded to defend him absolutely awfully. Salah is good enough that he will score no problem against idiots like that.
He also has that luck though of the ball falling to him in just the right place, perhaps it's just his natural movement that gets him there.
If you mark him tightly and don't give him space though you can shut him down fairly well (see young)
People saying he's on Messi's level are jokers though. The 3 of Mane/Firmino/Salah has great balance and all work really well together.
Seems like they gave him plenty of respect and marked him tightly, to be fair.