That’s a good question; it certainly is subjective–but the number of people who see him as creepy (or more usually, sleazy) is amazingly large.
I’d say that there’s something about the actor’s way of carrying himself and speaking that seems to signal, er, moral flexibility. But, again: that’s subjective.
ETA: I’m guessing that the Trivago people are aware that their spokesman strikes people this way, and they like it because they want the association to be “*hotels…hmn…exciting, transgressive sex!” *Or something like that, anyway.