the estimated mining cost for bitcoin after halving is around 12 ~ 15k, probably that's why miner/tether/exchanges are so desperate to pump it to that level

i speculate there are a scary amount of IOUs in the crypto market uses BTC as collateral, especially by miners. so this pump might not be just a simple pump and dump scheme, it's probabaly a life support for this market. Same as Fed buying junk bond

if a significant number of miners become unprofitable, they will default and sell, Tether will also have a hard time to maintain the peg. Since not only BTC value schrinks, all those BTC collateralized IOU will default, which, i suspect, makes up for most of tether's "reserve"