It’s either a toe issue or a negative camber issue. If it happened in a short amount of time it’s a toe problem.
If it happened slowly over a long time and the tires look tipped in at the top it could be too much negative camber, but it would have to be more than -1* of camber and that would be obvious just looking at the angle of the tires. Even with -1* camber the tires looked tipped in at the tops, and -1* won’t wear out the tires.