I know the point you are talking about with the missed shot. It was an aggressive backhand crosscourt that Medvedev hit from about 3/4 court that went long. It didnt miss by that much and given how good his backhand had been there was nothing wrong with the shot selection as such. He was just slightly too aggressive with it.
That point was right after Nadal had got it to 15-40 after that ridiculous drop shot.
The other break point that Nadal saved was partially a result of poor shot selection by Med that drew Nadal forward and gave Nadal some opportunity to wrongfoot Medvedev by faking to drop shot but instead knifing a low dirty slice deep that tangled Medvedev up while he was charging towards the net.
Med didnt play the big points as well as Nadal in that crucial game but it definitely wasnt a choke. And the momentum swing itself was kickstarted by Nadal's outrageously risky dropshot wasn't it really?