Unpopular answer:
Shorter time limits. I played a 5 man once with 3 minute game limits. At first, there were a lot of stales, but later on, everyone hopped up the pace.
Unpopular answer 2:
Limited paint format. I have never played one, but it seems clear that when there is no ability to camp and dump paint, people must move.
I imagine that better players with more situational awareness and superior athleticism also contribute to faster more aggressive play.
I wonder whether cheating guns would? If they are easier to shoot on the run, would people be more apt to use that advantage to move, or would the higher rof be used to shut down lanes so effectively that people would be unable to make moves?