I asked this before and I still don't understand it: Who is holding the Tethers? I can see that "someone" wants to artificially increase the BTC price by buying

I asked this before and I still don't understand it: Who is holding the Tethers? I can see that "someone" wants to artificially increase the BTC price by buying BTC using USDT. But for this scheme to work, someone needs to sell BTC for USDT (and hold the USDT!). Who would do that and why? We are talking of about 2 billion USDT that have to be somewhere.