Especially with the Jay-Z connection I thought they were always seen as the most likely place he'd end up other than Cleveland. That's not really what a "sleeper" is. A sleeper would be like, if Milwaukee or somebody nobody expected had quietly put together an awesome pitch for Lebron.
Other teams would have to put together the chance to sign a few other big players, but the Nets have been doing nothing but angling for Lebron for years now. They want him to be the first face of the Brooklyn Knights and that has been the plan practically as long as they've planned on moving.