Nole was too passive in general throughout the match. (even desperate at times)
I think his abilty is there, fitness is getting there, but mentally not quite tuned in just yet.
Yes, he was playing with too much margin and when it got tight he didn't go for his shots. He was going cross court pretty much all the time and was afraid of changing the direction of his shots and put more pressure
Like BH DHL but that hasn't been working for him so when it got tight he was too afraid. Still though he was in many positions of taking that 4th set, at 4-1 up he had 3 BP opportunities, crazy momentum to go with in that 5th set. At 5-3, he was 30-0 up, but lost 4 points in a row to get broken back. Then in the TB multiple set points with the most notable one when he framed his shot wich should have been an easy put away.
I'd say it was a combination of low confidence in tight moments but also bad luck. However that point where he framed his shot was just pure bad luck.