Buttler dropping Masood on 45 is the decisive moment of the test but this match is a pretty good case for why Root is not cut out for captaincy. There have been 3 notable phases within this game where Root has not quite sensed the opportunity or ensured that he's applied the maximum amount of pressure.
Day 1, evening session: Letting the umpires force him to bowl 2 spinners to Babar Azam, it cost England 17 runs when he could have dug in and forced them off for bad light.
Day 2, afternoon session: Pakistan are 187/5, there are 5 overs to the new ball and Root decides to turn his arm over with Bess for those 5 overs because even though he has 4 quicks he cannot deviate from the idea that you must bowl some part time rubbish before taking the new ball. Pakistan score 27 runs and Shadab settles into his work.
Day 3, evening session: Pakistan are 63/4 and England have a window. It becomes clear after 6/7 overs that the Pakistani batsmen are quite comfortable with Bess, more comfortable than they are vs the quicks. Root bowls him for about 4 overs too long whilst replacing Woakes with Anderson who has been England's worst quick so far. In the end Root has to call up his talismanic all-rounder, who is not quite fully fit, to get him out of the shit again.
It's harsh on Bess that a lot of the poor decisions centre on bowling him but that is what happens when you don't choose your best spinner. If Roston Chase is spinning it more than your main spinner you should be thinking long and hard about if he's the best spinner you have. Bess is 22 and has loads of time on his side, they're treating him like he's a spin prodigy when he's not even the best spinner for his county.