It's obfuscated by splitting the components into multiple cryptocurrencies with multiple actors, but that's what's going on. People were staking UST for 19.5% returns, and if you cut through the fluff, those returns came from later people putting their money in hoping to get those returns themselves. (and because UST was a stablecoin those returns were (ostensibly) in dollars, not just inflation of the coin value)
>>Khoth+(OP)
You just described banks. Banks take deposits & lend the money out at a higher rate. This is what anchor protocol was all about. Pay high interest, and lend at even higher interest.