I don't understand cryptocurrency markets at all, but, could there be something where the only people participating in the USDT market are those who are at least somewhat confident that USDT is what it claims to be and therefore are pricing it at $1?

What do you get out of participating in the market if you expect Tether to be fraudulent? You'd personally price it at zero, then, right? Can you profitably short it, or does everything just break down if you're right?

That is, if you hold USDT and want to sell it for cheap, who is going to buy it for cheap-but-nonzero?