Pop has a quality that endears him to the players.
He treats everyone the same.
This, combined with the franchise located in San Antonio, has eliminated some free agents from consideration. SA's locale had more to do with it. But he won't woo a prima donna.
At first, he took a system and got the players that could live in it. He did quite well.
Lately, he's adjusted the system to fit the players he had. He's always tried (and still does) to push the defense first mentality, but he ALLOWED for an offensive team based on the talent.
I lived with Adelman (as a Houston resident). I'd take Pop with those teams. Scola damn sure would have learned how to defend at least ONE set play in the NBA. Which would put him a step ahead of where he is now.
As for Phil, Pop never quit when the team stopped winning. He never looked for the next ideal opportunity. He doesn't seem averse to failure.