I think you are thinking more of defense contracting than darpa.
Also, darpa has real use-cases and those use-cases tend to be hard to solve ones, they aren't VCs looking for the next trend to vampire like a national security version of the TV show shark tank.
Granted, it is 2023, it is the govt, and it is tech/eng/sci holy trinity of profit so I wouldn't be shocked if I am off the mark with my assessment.
Maybe. Even when a PM is very technical in their field, they are not expected to know the nitty gritty of the broad area they tackle in a program. To come up with realistic programs and execute them successfully, a PM needs to know where are the boundaries of current knowledge, how much $$ is required to push research to transition to real tech... and sniff out bullshit being sold by research labs. Bullshitters or not, they need to be really good at sniffing bullshit!