It simply goes like this, Tether minted USDT out of thin air, billions->investors buy them->then buy Bitcoin pushing the price higher. At least this is one theory of out the many and there are speculators who think that this is what's happening in the market right now as we have seen a push above $73,000 new all time high for Bitcoin.
Also there is a question on how Tether is doing this as we have been suspected that they are running on fractional reserves, a (mal)practice by many big banks in America.
I think Tether's minting of more USDT is positive for BTC and the market because it shows that more money is flowing into the crypto market through stablecoins. As the cap of stablecoins increases, the buying pressure on crypto will increase and drive up the price. Stablecoins are like the lifeblood of the market, the more stablecoins there are and the more actively they are moved, the more the market will develop.
What you mentioned about Tether minting USDT out of thin air to pump the BTC price is probably a story of the past, in 2017. Now, it has become more transparent and no one has enough evidence to accuse Tether of this crime. So, I still choose to trust Tether and USDT so that I can focus my mind on the investment process instead of being suspicious
