How come whenever a show has that one goofy snarky male character that is super likable at the start of the show, a couple seasons in they'll have more than likely morphed into a petty douchebag?

likely, I feel this happens at least 70% of the time

And usually the writers seem to try and frame it so we'll be sympathetic with them. "Oh, he's such a nice goofy guy who just gets shit on by the womenz. Oh poor him. It has nothing to do with his shitty behavior."

Either that or they become way less snarky and goofy