Hubris. This is why this team lost. Hubris. Hubris in thinking they are 234.66% better than they really are, that they can play lackadaisical at the start because they were playing a weakened, demoralized team missing Luka (permanently) and AD (temporarily) and shooting nearly 50% from 3 so no need to defend. They thought they didn't have to pay attention to 70 year old Klay Thompson or washed-up has-been also-ran Spencer Dinwiddie who combined nearly put up a half century of points against them. 21-0 in fast break points when the game was still a contest...embarrassing. Tatum -22, Brown -15, nothing says I don't care about this game like their defensive effort in the first three quarters. Let the Mavs shoot 60% from 2, yes that happens when you turn the ball over 14 times and don't run back to defend.
The bench guys tried to put lipstick on a pig at the last but this was a "I don't care, this is a meaningless game, we showed we can win games when we're switched on like vs Cleveland, if we play this team in a 7 game series we will beat them 4-2". And they would be right - they probably will beat this team 4-2 when they have their heads screwed on right. But it's still hubris.