As a corollary, I think if something is utterly useless but cool, it's usually worth giving it a second look.

Who, for example, would create a demoscene program or anything like that but for the coolness and the desire to show off?

I object to your essentialism. Presuming monolithic psychological characteristics, motivations, or behaviors from someone’s academic degree is just as false as presuming them from someone’s skin color, race, sex, gender, occupation, age, or other observable characteristics.

I’m sure you meant no harm, but think you can do better than giving into simplistic base rate fallacy thinking, especially as you are also factually wrong: arguably there isn’t a single big, bad wolf tech company that was started by MBAs. In fact, two of them were started by Harvard college dropouts and one of them by Stanford PhDs. The big tech companies I can think of that were started by MBAs (eBay, grubhub, intuit, Bloomberg) are arguably much less harmful, though two of them became quasi-monopolies.

The problems articulated by the commenter are much more likely the result of institutional failures and skewed cultural incentives than the result of a class of people or a “cabal” (the word implies conspiratorial coordination and scheming).