Just rummaged through all sorts of junk and came across this interesting story ;)
1 USDT is printed without fiat backing.
2 On the "ghost" USDT, bots buy bitcoin at key levels, and the bots push its price up.
3 While bitcoin is growing, the guys from Tether/Bitfinex withdraw the BTC bought on the lows to their wallets.
4 When the price reaches the required level from above, Tether/Bitfinex sell bitcoins from OTC wallets for real fiat.
5 Part of the fiat received goes to Bitfinex/Tether profit.
6 The remainder forms a fund from which payments in fiat should be made to Tether clients who decided to exchange USDT for USD.