Ask HN: How advanced is military AI?

I was watching a documentary about military defense systems and the autonomous capabilities of some of the US weapons caught me off guard. For example, the Phalanx CIWS is a minigun that protects ships from incoming missiles. It can identify and destroy planes and missiles on its own without human intervention. It makes me wonder about how the military achieves this economically. I thought government jobs pay less than a cushy job at Google. But at the same time, you need to keep your brightest minds working on defense. How do they do it?