The Atlanta team he inherited had already plateaued and there was rebuild work he and Ferry did (where is Josh Smith these days?) after he got the job to keep them relevant. That team that won 60 games and made it to the conference final had a heavy Bud influence (Millsap, Schroeder, Bazemore), but that was also peak East being trash era. He left after the management drama unfolded and this new group made it clear they were going to stick with a cheap draft rebuild despite early chest-beating to be luxury spenders: there was money for Dwight (a horrible decision on Bud's part, to be honest, to agree to that signing) but not Horford, even though they would have stayed under the cap to keep him. Then trading Korver sealed it. It is a bit unfair to hold an ownership change that stripped away the roster from a coach that was signed and paid (expensively) to be a contender.

How he got the Bucks job over whatever other candidate is another question, but he certainly hasn't failed there.