> Also, there is nothing which proves that Tether actually isn't backed by anything.
There is a lot of circumstantial evidence though. To wit:
* Tether was previously caught lying, in a manner that is attuned to how many big frauds start (you hit a small road bump, so you lie to cover up the road bump, figuring you'll be able to make up the shortfall before too long. But now your lying projections are going faster than your ability to catch up, so what was originally a "small" lie is now a "big" lie). Tether had had the cash, until it was stolen from them, and they started lying to pretend that it wasn't stolen.
* Notably, Tether has yet to provide any audited statement of their claimed finances, in over 4 years. Even the attestations that they have come out with don't actually provide much in the way of reassurance.
* Their claimed asset breakdown, the closest thing any of us have to being able to being able to validate their claims, is presented in the form of 2 pie charts with vague labels, one of which is so bad that no one knows what it's supposed to mean ("reverse repo notes").
* Doing the math in the above point, they claim to be one of the largest consumers of commercial paper. They haven't said whose commercial paper they're buying, and no one has reported transacting with them. Supposedly this is for privacy, but it is the standard in the entire industry to just list all of your holdings for transparency's sake [1].
* Also, Tether has increased its issuance to the tune of several billion dollars a month. That's the kind of extraordinary claim that requires extraordinary evidence to back it up.
[1] Unless you're Bernie Madoff and you're promising awesome financial returns with your secretive trading strategy. Except it also turned out that said strategy was a literal Ponzi scheme. Note that "we're not telling you what we're investing in" is generally one of the red flags for a fraud.