Autonomous ground vehicles were funded by the DARPA grand challenge, and the motivation was explicitly military[1]

[1] Rational subsection of the Background section (section I) in this pdf: https://www.esd.whs.mil/Portals/54/Documents/FOID/Reading%20...

The whole thing is worth a read too, it explains all the other military use tech that will arise from the self driving car ecosystem, further justifying the investment.