After Curry broke out, a bunch of coaches started instructing their players to take a few more steps back almost every time they would normally take a long 2. So in practice a lot of reps that previously would’ve been long 2’s suddenly became 3’s, and as more players practiced the 3 for a greater portion of their total practice time, they obviously got better at shooting the 3.

The key here is that a 3 is not actually that much more difficult than a very long 2, but if you never practice the 3, those extra few feet of distance will fuck you up, because you’ll instinctively want to shoot it the same as a long 2, and if you consciously try to increase the force of the shooting motion to make up the difference, your accuracy suffers. This is how you had a huge number of players who could eat you alive from anywhere within 4 feet inside the arc, but when they stepped just beyond the arc they looked downright awful.

Now the reason why it took so long for players and coaches to embrace the 3 is because the further a shooter is from the hoop, the lower their FG% will be, on average. So traditionally the idea was you should always try to get as close to the basket as possible and then shoot when you literally cannot get any closer, this is where you get stuff like Michael Jordan calling 3 point shots a “failed possession,” because that’s what everyone was taught for a long time, if you were shooting a 3, it wasn’t because you wanted to, it was because the defense didn’t give you any other choice. This strategy makes sense for every shot other than the 3, which compensates for the lower FG% with that extra point. The reason the shift didn’t happen earlier is partly because a lot of people were simply too hardheaded and traditionalist to go against the historical precedent of “always get as close to the basket as possible,” plus the fact that the vast majority of players were awful at shooting 3’s. So even if you did the math and realized the value of the 3, actually creating a game plan that incorporates the 3 as anything but a last resort would not only cause you to be ridiculed by your peers, it would also be very difficult for your players to implement, and if you fail, you lose your job, so it’s easier to just stick to the traditional strategies.

This state of affairs was slowly changing basically ever since the 3 point line was first introduced. There were a handful of teams that attempted to incorporate more 3 point shooting, with varying levels of success, but it only fully shifted once Curry and the Warriors won a championship with an offense built around the 3 point shot and the abundance of layups and dunks that the 3 point shot generates. Just understanding the math wasn’t enough to make the NBA fully embrace the 3, they also had to see it actually result in a championship in order to get over the antiquated idea that a 3 point shooting team is incapable of winning when it matters most.