Same reason there’s now a separate cyber branch. There are completely different strategies, tactics and technologies involved. The procurement of those is completely different. AFAIK, there’s no much at DARPA for space, unlike for cyber. I have no idea how we’re going to pull our butts out of this fire, but it is long overdue.
The US military has always had a parallel space program—with NASA as the cover.
Seriously, folks, you don’t believe the lies of the MSM on anything else—why would you believe the cover stories on this topic.