ponzi is a scheme in which Peter money is used to pay Paul.
It is not just that. Bitcoin is counting on new money entering, just as Ponzi's do. When no new money enter Willy bot and Tether take over. Who will pay the 10 Billion USDT?
That doesn't make bitcoin a ponzi.
Tether is the ponzi scheme here. Don't get confused. The end-result might look similar but bitcoin will recover from tether and survive while tether itself may disappear anytime.
I also do not understand how a paranoiac country like the US is letting Bitfinex to get away with this. The only possbility comes to my mind is, they are purposefully letting them scam people.