The Holloman Pact made the alien technology transfer contingent on launching an alien-human hybrid program. You see, the Zeta Reticulans mandate their technology to be stewarded by hybrids (similar to how China requires a 50% Chinese joint venture to gain access to their markets). The two species' geneticists started working together, and in 1971 the first viable hybrid was born: Elon Musk. Then we had to wait for the hybrid to mature, before it could be given stewardship of this sensitive technology. Meanwhile a generations-long cultural manipulation program was also underway, to prepare humanity for disclosure.

Of course it's sarcasm, but if it WAS true, it would be because the government was working in cahoots with all those defense contractors all along, until the Trump administration came along and decided to privatize it, at which point SpaceX seized its opportunity.