These "breaches" are such a regular occurrence for T-Mobile that one could suppose that they are intentional and that T-Mobile may be getting paid for the data, kinda like a side hustle, where they constantly troll for n00b customers who either haven't been part of a previous breach or who have managed to lay aside their disgust and take the low price deal so they can get pwned again.

If I ran the show I'd bankrupt the company and its management.

Never attribute an unfortunate outcome to incompetence when the possibility exists that it was caused by greed.