I have been watching the same clip for months and until now I had not stopped to try to understand what was happening in it. The only thing I could think about was how overwhelming it would be to see someone play Super Mario Bros 3 that way. chaotic.
Today I came across the explanation behind that surreal game and now I’m glad I came across it. No, it is not that the player behind said game is completely crazy and has a superhuman ability, is that he is not a player per se.
What we see in the video is an example of what the wonderful world of the TAS (from Tool-Assisted Speedrun) or tool-assisted speedrun. And yes, behind him there is an expert in the game, but not anyone playing in real time.
The idea behind this method is to take a game to the last consequences in an automated way. The creator of the TAS tells the game what to do in each frame to bring to life the most perfect game possible and, in this way, demonstrate what a player with sufficient skill and knowledge could do in each phase.
Here is another video with a game TAS in Celeste that completes the game in just 20 minutes with a precision and agility that mortals will not reach even in our best dreams. Damn machines, they beat us almost to everything.