This guy had illegal access (granted by Trump) to the Treasury's payment system including access to SS numbers, addresses, birth dates and so on. He had both read and write access meaning he could have left malicious code in there.
It turns out this guy just isn't unqualified and had illegal access, he was also a proud racist and expressed enthusiasm for eugenics.
https://thehill.com/business/5131442-elon-musk-deputy-resign/
Is everyone in Elon's orbit a flaming Nazi?
The government is going to end up paying billions of dollars out to the victims of this security breach.