+/- at team level is just the winning/losing margin? Thats not instructive of why a team won or lost, its literally the score. Its like saying, they lost because they scored less points.
I don't think you've captured the metric that shows the real difference though. Nothing fancy, just FG%.
Sixers, 39.3% on 89 attempts. Raptors 51.9% on 79 attempts. The Raptors completely outshot the Sixers.
In the regular season the Sixers averaged 47.1% on 88.2 attempts. Raptors 47.4% on 89.1 attempts.
For the playoffs as a whole the Sixers have averaged 44.2% on 92.5 attempts. Raptors 48.5 on 83.5 attempts.
Take out Game one and its 49.3% Sixers, 47.86% Raptors.
The question is, did the Raptors do something special to cause the Sixers to miss so many attempts or is it luck based, and vice versa, did the Sixers allow easy buckets, or did the Raptors get a huge slice of luck?
After the Nets game 1 there was a lot of hand-wringing among sixers fans even though the Nets had huge a crazy game from 3 and the Sixers couldn't make a shot. Once that returned to normal the Sixers dealt with the Nets (relatively) easily.
I'm not suggesting the Sixers will rebound easily in the rest of this series. I don't know enough about basketball to say that and I definitely don't understand defence enough, and it looked to me in game one that the Raptors were much better on defence than the Sixers. Regardless of how the series ends I think the FG% will end up closer to season averages by the time it ends.