paul george isn't a real superstar, and his team is as weak-minded as they come. a couple years ago they twice blew 10-15 point leads in the last few minutes of games in a playoff series that they ended up losing.
but with that being said, a lot of miami's "confidence" comes from the officiating, much as jordan's bulls and shaq's lakers did. this is why they melt down and start with the dirty plays whenever they're losing - they're little more than spoiled children. several times a game they commit obvious fouls on defense and then break away for easy points. it doesn't sound like much, but if the refs give them just three of those plays a game - three more than the other team - then that's six points, and in this league it's a lot easier winning with a six point head start.
that still doesn't let george and co. off the hook though for their bad body language and lack of aggression late in the game. it's not just nerves, the pacers don't trust each other and they don't believe in themselves. they don't deserve to win.