That is my reaction as well...just don't get it.
She spend a couple of years as Chair of the CIA's External Advisory Board. She likely also knows more about computer and cybersecurity than anyone else being considered.
But I don't think it is just expertise -- I think it's just her brain/work ethic. She seemed as or more knowledgeable than any of the guys on that stage when it came to foreign affairs. Honestly, that impressed the crap out of me.
It would be an outside the box pick, but I'd really like it.
@mystery-ak @Oceander Also found this 2015 National Review Article called "The CEO and the CIA", about her work with the CIA. Can't figure out how to copy it, but here's the link. Definitely worth a read, and given that she was a Chair, which is somewhat analogous to what the DNI (as opposed to the DCIA) does, she actually seems like a good pick.
http://www.nationalreview.com/article/417938/ceo-and-cia-jim-geraghty