"A booming industry of cybersecurity consultants, software suppliers and incident-response teams have so far failed to turn the tide against hackers and identity thieves who fuel their businesses by tapping these deep reservoirs of stolen corporate data." Sure, blame the consultants with their "booming industry". I'm sure T-Mobile spent adequate amounts of money on securing their data, hired all the best people, and…
I'm sure it's both. As in, much of what they did spend likely went to snake oil salesmen. I've met lots of security consultants who did not have backgrounds in math or compsci.
I'm going to bet that they did have qualified engineers, because I like to assume the best in people, but I also assume that those engineers may not have been able to make the changes they want to.
In my experience in big companies, corporate bureaucracy and a complete unwillingness to change processes or systems is usually a bigger hinderance to security than the skill level of consultants/engineers.