Yeah, I agree I don't think he was really being used all that badly. He didn't win a ton of matches, but they definately gave him opportunity to showcase his talents.
My guess would be he got frustrated for not being called up to the main roster after all this time and wants to be a bigger star than he is now. Because while I do beleive WWE will continue to use him, he's likely going to be more a Cesaro than a Roman Reigns or a Seth Rollins. A good worker who will get his abilities showcased, but won't necessarily get pushed to the moon.