The culture that has been maintained over the years of individual ego being subsumed by team success. Particularly noticeable with guys like Parker and Ginobili who could have been lead stars on their own teams.
First to analytics with the corner 3 and especially with defensive innovations guiding opposing teams to fill up on bad shots. The spurs changed the league; the Morey rockets and Kerr warriors are the next step in that trend.
First to really mine the international market for underappreciated talent, which is how they snagged Ginobili, Parker, and many other players well below where they should have been selected.
First era, 1997 to 2005, was all about stifling defense and running the 4-down grind on offense. Made a complete stylistic change to guard-centric pick-and-roll offense in 2006-2007. Then in about 2013, shifted to the free-flowing, fast paced "beautiful game" offense with no center of gravity, tons of off-ball movement, and half second pass/shoot decisions. He won titles with all three styles and largely with the same key players, and did it against the Shaq/Kobe Lakers, the early oughts Pistons, Nash/Stoudamire Suns, LeBron Cavs, the Heatles, Nowitzki Mavs, and half a dozen other great teams.
To me the last title is the one that really cemented his stature. The key players were all either past their prime, before their prime, or Patty Mills, and they destroyed the Lebron Heat. They were fast paced run and gun with unheard of offensive efficiency, but still throttled people defensively when they chose. No one played 30 mpg and TP led them in scoring with less than 17 ppg. This was the style Kerr adapted to Golden State.
Pop's coaching tree includes Brett Brown at Philadelphia, Mike Budenholzer who has now won CoY at two different teams, Borrego at Charlotte, Quin Snyder in Utah, and a few other former head coaches.
Right now Pop is struggling with too many low efficiency, no defense, ball dominant iso players. For the first time his team physically looks like it should be good, but it doesn't have the intelligence and focus of those title teams. He has to take some of the criticism for that, but i never expected a team with Aldridge, Rudy Gay, and DeRozan to be much good. It looks like something the Knicks would try.