I gotta wonder about the psyche of a pro athlete here.
There's got to be a level of arrogance to make it to the top of your profession. Most players at this level get there by thinking they're the best player every time they step on the floor. "If any team is going to come back from 0-3 in the Finals, it's going to be us!" and "we just have to win one at a time." I can get behind that thinking. Also Kyrie was part of a 3-1 comeback against an actual Goliath in the 72-win Warriors, if anybody knows a comeback is possible, it should be him.
There's also the pride element, "no way I'm going to let the other team sweep me" and/or "I'm not going out on my home floor." I can get behind either of these as well.
But then there's the human element too. "We're down 0-3, the series is practically over, why would I want to extend this a few more days, just put us out of our misery." And do you really want to win on your home floor, just to fly out to Boston to lose there, and then have to fly back to Dallas (or wherever you call home)?
Anything could happen this game (close game or blowout) and I wouldn't be surprised.