You are not missing anything. It's has a death spiral in it by design. If luna price goes down, then people lose trust, then people start selling ust, which leads to burning ust and minting more luna, which inflates luna supply, which makes luna price go down, which makes people lose trust more, etc.
And it gets faster and faster as luna price falls, because more luna is minted to burn the ust. The amount of minting is inversely proportional to luna price.
And it gets faster and faster as luna price falls, because more luna is minted to burn the ust. The amount of minting is inversely proportional to luna price.