USDT is interesting. My guess is they have less than a 1 for 1 reserve, but the entire US economy operates on something like a 30% reserve (last I knew), so if Tether is running a 90% reserve I could see why they would never want to share this. But then also, a 90% reserve is unlikely to bust, ever.
So at that point it's a question of what their reserve is, and whether it's viable. Since they make money doing this, and it's a legit business model to offer a 1:1 peg, their economic interest would be not to go full ponzi and take the money and run. I would wager it stabilizes, news articles by crypto people tend to over-emphasize issues. And the USDT drop is a simple by-product of the bank deposits not being accepted.
Bank deposits getting no longer accepted by Tether, are usually because whatever country the bank deposits were being sent to, decides that there might be "money laundering" or some other unfair classification of crypto applied to the money, and so they freeze the funds presently in that bank, and so Tether stops deposits. Because the money would be stuck there. This does cause a temporary price drop due to loss of confidence in the system. It's likely caused by people who buy tether to exchange it into fiat so they earn arbitrage, they are assigning a higher risk value to the exchange so they lower the level they are willing to buy at.