I don't watch basketball, so I am speculating, but isn't this a case where defence hasn't yet adapted to the new attacking strategies? Wouldn't you expect that in a few years teams will be better at defending against 3s, reducing their expected value and therefore swinging the pendulum back towards more 2s?
The Nash equilibrium should be that the expected values of 2s and 3s are equal. If you're off, you would expect a trend toward that equilibrium, possibly with some overcorrection.
