I agree that Tether has certainly been pumping BTC with money they don't have, but
> if you look at recent (~1.5 years) sudden spikes in BTC price, they correspond almost always to a new supply of USDT being released by Tether.
is what you would expect to see even if Tether was 100% legit. As you say, most BTC liquidity is in USDT, so people buying Bitcoin would first buy (mint) USDT from Tether, and then use that to buy BTC.
> if you look at recent (~1.5 years) sudden spikes in BTC price, they correspond almost always to a new supply of USDT being released by Tether.
is what you would expect to see even if Tether was 100% legit. As you say, most BTC liquidity is in USDT, so people buying Bitcoin would first buy (mint) USDT from Tether, and then use that to buy BTC.