Guys like Lesnar, Kane and Yokozuna also got the world title after mere months in WWE but people don't seem to sh!t on them for it.
Dude, those 3 guys are unique, Sheamus is just a mere replica, he is ... generic.
While I don't think being a Trips guy helped him, I don't think it's the main reason why he's not as popular as you might like.
His booking has been HORRIBLE since he came back and I think his feud with Christian hurt him a great deal.
He was unbeatable during that feud, except of having some back and forth in the W/L category he was winning all the matches clean. People who were still on the verge of liking/hating him went into the worst spot you can be about someone : the "I don't care" category. He's always winning and being dominant. It's boring.
Plus he is a man of a few moves, fans don't like that anymore, well not from guys shove down our throats.
Lesnar was a never before seen monster AND a Paul Heyman guy
Kane came in the biggest storyline at the time and the story telling in that feud was awesome
Yokozuna, while I'm too young to remember exactly his debut, people wanted to see that guy and all of his match were a big deal, His body and uniqueness at the time made him a star.
Sheamus has no manager, has no "never before seen" feel to his character, doesn't have a great feud and people don't care if he's on the show or not.
Recipe for boooooossss