De Minaur melt down

Someone please enlighten me on this one?   He won the first set in 19 minutes 6-0.  Then proceeds to get monkey stomped the next 3 sets by a guy who collapsed 2 days ago and couldn’t walk?  

I wouldn't put too much stock on Mensik cramping up 2 days ago he's young and it wasn't an actual injury, I'm not shocked he's recovered. I took the under 36.5 on this match thinking Demon was going to steamroll but this is just really great play after that first set. I saw Gill Gross said this after Sinner went out, some food for thought

"This is just like the 2020 USO. Everyone in the draw suddenly knows this is the chance. Djokovic the only former major champ remaining. Expect the nerves to be off the charts in these matches. The tennis in New York that year was some of the ugliest you’ll see. Pressure is on."