WWE has a new policy that any main event face needs to be a goofy corny suck-up. Seamus is up there with Cena now and I guess they want to give Miz a push too. Difference is Miz and Cena at the very least can act and are more believable in that you can buy that they believe in what they're saying, no matter how bad it is. Seamus comes off as knowing what he's saying is god awful so his delivery isn't as believable.
I don't think he's anything special anyway and they actually seem to have toned down on his jokes but eh. Wouldn't mind if he fell back down the card a few steps.