Has been clashing with Kegseth for months and just quit.
There's speculation it's connected to the leaking that Iran did significant damage last night hitting US targets over there that we had not made public, including leaking pics of it. Not saying Driscoll himself leaked it he's actually a civilian but that the issue between Driscoll and Hegseth appears to have led to someone being so pissed off they leaked the damage Iran had done to make Hegseth look bad