I don't know how massively unemployed economy would work, but I guess the corporate elite locking themselves into an economical bubble where they only trade with each other and some other remaining employees isn't that crazy.

I just know that UBI itself is also a pretty crazy concept. If you gave every adult in US $30 000 a year you would need 6.27 trillion USD, which is coincidentally the exact value of US government budget for the 2022 and they're already in deficit. And that's only $30 000 a year.