Put on your game face, put on a show
A fundamental factor in Detroit Metal City's appeal is not so much the outrageousness but, as in all comedic acts, that the engineered coincidences line up and the perpetrators get away with it. Krauser wins, even when he loses.
With the rapid-fire line delivery and scene cut overload, it's not that DMC is channeling evil so much as it's channeling Shinbo. A lot of the antics, and even the colour selection, would not look out of place in something like Zetsubou Sensei. But Nozomu Itoshiki is always wrong, even when he's right.
Anyone who finds the stage irresistable will identify with Negishi. The way things seem to spiral out of hand whenever there's a bunch of crazy people to push him on, is a situation that plays out all the time in less extreme forms, even when alcohol is a non-factor.
As an insecure music student, practicing in a vacuum was a slog. Always selling short any progress made, the hardest person to impress tends to be yourself, and so in a twisted form of reasoning, there is zero motivation to try. When there's someone else in the room that's not your parent, motivation goes through the roof. All it takes is one.
Bonus points if that person is also a music student, and you're in the process of one-upping them. Nothing personal, it's just skill. The less charitable would call it ownage.
Where you see someone practicing, I see a challenge. Even if they're just noobing up scales. Shy, nervous wreck suddenly becomes Minute Waltz God. Also incredibly arrogant.
It seems quintessentially human to hoist yourself up a metaphorical ladder, even if means that the rungs that you step on are other people.
There are those of us who laugh at Jekyll-Hyde Negishi-Krauser because the transformation seems so ridiculous and jarring, and then there are those who laugh because it is, or was, our existence. "Nicest person you could ever meet, but has a bit of a competitive streak."
Just a tad.
P.S.
DMC's structure, with roughly 7 minute skits with clearly defined breaks, goes a long way towards not burning out a marathon viewer.

