I always felt the Spurs operated like a successful family owned business, as opposed to either a corporation (Raptors) or a family business ran by nepo babies (Lakers, Kings). They understand some of the disadvantages of the market (comparatively small, lower income levels), and so they looked at other aspects, understood the fan base and marketed accordingly.
I would say some of these superstars that we had over the years helped immensely as well. Obviously the Admiral got a lot of the credit from starting all of that with his general team focused selflessness and lack of ego, then there is Tim with his no-nonsense approach, Manu with his focus of team and sacrificing his own stats, and Tony changing his game to buy into the team, but I always felt the OGs like Gervin, A-Train, Silas, Moore and bunch was just unsung with how they approached the game.
Pop solidified a lot of these aspects by being a leader.
It is hard to find athletes who has that mentality. As much as people disliked Derozan, I always felt the guy wanted to do well and was team focused, too bad his game was just dated and was being phased out in the new NBA.
A system where Pop changed the system to fit the players strengths (driving players to the baseline by taking advantage of the Twin Towers), 4-down (I know) by taking Duncan's low post dominance and then having shooters around him, shifting to a drive and kick offence with the emergency of Manu, having the ball in Tony's hands when he was literally unstoppable driving to the lane, then implementing the beautiful game when we had players like Diaw and Splitter to take advantage of their collective IQ.
Then of course, there are alternative and innovative ways and looking at all aspects of the operations. Scouting players overseas, having a shooting coach (what happened to that?), embracing different cultures and wisdom from people of different backgrounds, minimizing long 2's / mid range, moving to analytics based games, team dinners, knowing people as people. A lot of these are being copied around the league now and that speaks to the impact the Spurs have.