The Spurs got Tim Duncan, one of the most solid pieces in NBA history to build a team around. Add a great draft strategy and Pop and success is hard to avoid. Their team was built around 2-3 players who contributed heavily with alot of interchangeable players around them. The Pistons had 5+ players all contributing alot who fit very well together. Because of the synergy effects those players weren't interchangeable at all and it's harder to keep 5 players than 3. It also seems like the Spurs had more of a red line in everything they did. However, I'm pretty sure things would have looked alot different if they would have got Van Horn instead of Duncan.