The reason for this team’s 4th quarter collapses can be attributed to Coach Stevens’ flawed strategy (dating back to Butler).
Stevens’ defensive scheme, generally, involves constant switching of the on-ball defender when picks are set. His offensive set, generally, involves 2 players standing in opposite 3 corners for optimal spacing.
Opposing teams are exploiting his strategy by resting their best player(s)/closer(s) on one of the static shooters in the corner and, on the other end, the relatively fresh star player can reek havoc on the offensive end.
Meanwhile, Tatum/Brown/Kemba are burning the candle at both ends, in his switch-heavy, high-energy exertion defense; then running an offense where they have to take one of their other players, usually a good/decent defender, off the dribble and finish the play because passing lanes to the corner shooters are cutoff.
The opposing star player get to rest on defense and go to work on offense, while ours have to work their tails off on defense and offense.
For reference, watch the highlights of the recent 4th quarters against the Mavs and Hawks losses and count the times Doncic and Young are involved in an action or guarding the ball... they’re basically resting on a static corner shooter hedging toward the paint all 4th quarter. It should be no surprise when an opposing team’s star is draining 25-40 footers while our star players are putting up bricks in this “your turn-my turn” isolation offense.