Even if your figures seem out of date, your argument against UST also holds for USDT (which underpins much of the crypto price bubble):
There is 7B USD in circulation and the market cap of US(D)T is 74 BILLION USD
All this perceived wealth is going to melt into air soon, and yes a bear market has already arrived.
I personally have lots of misgivings about various crypto but I really don't have enough expertise to argue against someone telling me that I just don't understand and everything is fine.
Surely the onus is on those promoting such schemes to convincingly explain their workings; if you can get 20% a year the explanation had better be good...
This is just the last resort of a scoundrel who knows they can’t explain their scam.