Someone posted an interview with Terry about playing without Rondo and he mentioned that the wings were going to try a little harder to get up court so they could get more transition scoring. Couple that with the Kings being especially poor at transition defense and you'd likely end up with a good transition game.
You're probably right that this explains most of it.
Hopefully the Celtics stay committed to getting out on the break like that. They need to get as many easy opportunities as they can, since they're going to be a mess in the half-court.
Hopefully they do it next year as well.