Also as many have pointed out, Ben Simmons' downfall in philly started with passing up a layup out of fear of getting fouled. In the end of this last game, Joel Embiid passed up an open short midrange jump shot to try and draw a foul and ended up getting nothing.
So here's the play by play video for the play in question.
This is like, one of the worst misplays I've ever seen in a basketball game, when you factor in the level of the player in question and the importance of the moment.
This is an out of bounds play; the Sixers run a little action for embiid to free him from his main defender (Precious Achiuwa) on the wing. This action works perfectly; when Embiid catches it, he's completely alone. All of the Knicks defenders are occupied; Achiuwa is recovering to Embiid by going around the play and is nowhere near him.
Embiid shoots it from there all the time, often over defenders or when being closely guarded. He makes those shots consistently. This is a good, quick shot for the Sixers, and if Embiid makes it they then have a long shot but very real chance of winning the game.
But Embiid decides instead to drive into the paint. It seems very likely he was trying to draw a foul. The argument for making this choice is twofold. First, maybe the drive is a higher percentage play than the shot; maybe the 'safety net' of being able to get a call and go to the line if he misses it is worth it. Second, Embiid is probably looking for an and-one. That one extra point is a big difference in this situation.
If the Sixers score two, they're still two points behind and basically have to get a steal and score to win the game. If they score three, they are only one point behind; in that situation, they can intentionally foul and even if the Knicks make both free throws, they can still make a three-point shot at the end of the game to tie and send the game to overtime. So, you can definitely see an argument for passing up on this shot.
But Embiid doesn't drive into the paint immediately. Instead, Embiid chooses to fake. Now, this is what really takes this play into the realm of "wtf was he thinking". He's faking nobody in particular. No defender is close enough to him to either do anything to his shot or bite on his fake. If you're very generous, you could look at Achiuwa getting a hand up and say that the fake freezes Achiuwa for a moment... but this is a curse in disguise, as we'll see.
After faking, Embiid then chooses to take one dribble and hop step into the paint for a layup. The move Embiid makes is not really conducive to drawing a foul; he's not really so close to the basket, and he's dancing around the Knicks defenders to get to the basket. Brunson and Anunoby are there, but completely out of position to do anything about Embiid, so they don't even foul him.
Instead, Achiuwa is there to meet Embiid's layup. He's credited with a block on this play. The reason he's there is because he bought Embiid's shot fake; but he didn't get off his feet or contest the shot, he turned around to rebound the ball! As soon as he understands that Embiid didn't actually shoot, he starts moving to help under the basket and ends up getting this very clutch block.
Because Embiid has so much horizontal momentum, he takes himself out of the play after missing the layup. Nic Batum doesn't really jump for the ball, Josh Hart ends up flying in for the rebound, and the Sixers' last best chance to eke out a win is gone.
