I think 2 things went wrong, first one was the fact that they clearly did that for the shock value of the thing without truly any plans pass the battle royal. You could have put anybody in that spot and it would have been as good as Cesaro.
The second thing was they put him with heyman after his big win. The fact was sonce they really didn't have anything for him af mania and Heyman did have anything to do until summerslam because lesnar was taking one of his long break, they thought maybe if we put Cesaro with Heyman and build up some sort of rivalry by the end of the summer between Cesaro and Heyman, this would lead into a summerslam match between Cesaro and Lesnar. The problem they encountered was that they fogot that the fans wanted the face turn now and not in four months like they had planned so with the fans not caring about Cesaro because of some booking decisions, they just drop the whole thing and became the workhorse that he his right now.
Cesaro is kinda a rare bread of wrestler, were you put him in a single situation and he's can have a good match but looks just like any other wrestlers, then you put him in a tag team and suddenly he look like a superstars. I always loved cesaro in tag team situation more so then any single run he had. In my opinion, that's kinda were he need to stay for the time beeing because he shine way more in a tag team then anytime he's been on his own.