Can a hub casing be warped/bent?
Hub shells with pressed flanges, as opposed to being one solid piece, can do things like this. In such a case the press fit wasn't tight/solid enough to resist all the considerable forces on the shell, and it gradually came loose.

The bearing cups that most hubs have pressed into them can also come loose and cause a similar set of issues to what you describe.

Both are rare problems, although it's probably true that most or many pressed flange hubs can self-destruct like this if ridden hard or long enough.

If it's not one of the above, then I have no idea, other than maybe something went wrong with the machining and it didn't have proper wall thickness or something. But this would be a very weird failure from a one-piece hub shell.

Getting a new wheel is the only reasonable fix.