Dismissing the ECF result due to "hot 3 pt. shooting" from the Heat sounds like an excuse to me. Not only did the Heat have confidence from their coaching staff, the gameplan, and their star players, but the Celtics also assisted them by playing so poorly and predictably. If you don't seem connected on defense, wouldn't that give them an extra boost of confidence? If you're only pretending to contest and not actually running hard like the Heat always did, isn't that a confidence builder? People often say shooting is all about confidence. Throughout the series, the Heat players just seemed supremely confident that they knew they had a pathway to victory if they did X, Y, and Z. The Celtics, if anything, showed overconfidence in not coming out to play the first three games.
I mean come on, they had to have the dreaded "players-only meeting" in the middle of the series! You're in the ECF and you're still sorting stuff out? That's not a championship team.