He backed it up with actual product-building merit and enough (but not a lot of) reality-testing. His products were successful largely because of him. Too many copycats forget about the merit part of the equation.
Had Apple gone with Be instead, most likely all three companies would have gone bankrupt before 2000, and Pixar would be Jobs last successful company instead.
Where NeXT went wrong is in being astronomically expensive, which drove its addressable market to nothing. This is the exact same mistake Jobs made with the Lisa. The significantly inferior Apple II platform was far more successful.