The hype got out of control because he was the shining light in a sh*t show of a season under Moyes and off the back of that he got a great contract an anyone who'd seen this kid in reserve games could see that he was a serious talent. There was all the national teams fighting over him and his profile grew and grew but while he was fun to watch he wasn't actually doing much in terms of scoring or creating chances, he was very good at going on a nice dribble then putting it just wide it was obvious what the next step was for him and that was to improve his final product.
Think the years since that season have just been a complete waste he never really fit in with LVG he had that pointless spell at Dortmund and he was obviously sent to Sunderland just to get him out the club. I think Utd have probably been looking to move him on for a while now.
There are suggestions the money and fame went to his head a bit which is understandable and Utd played their part reportedly giving him a £60k a week contract, plus the number 11 shirt after Giggs retired but it felt like they didn't really have anyone there keeping an eye on him making sure he kept his feet on the ground. I think it's safe to say the club and his advisors haven't looked after him properly over the last 3 seasons and as a result his career has taken a bit of a nosedive, there's still plenty of time to recover but it'll be very hard for him to make it back to the very very top now.
This seems like a great move for him, I think the Spanish league is better suited to him as it's less physical and more technical and he might get his career back on track but I don't see him ever coming back to Utd.