I'm surprised at the rate of progress too. NASA used to be able to make rapid progress like that, but I feel like - from my layman's perspective - they couldn't do that now. It would cost billions more than it cost SpaceX to start from nothing (well, not exactly, they had help from NASA, but still) and take years longer.
I know people who work at SpaceX. They recruit pretty heavily from CMU (where I am now). From what I have heard, this is why they get things done so quickly: 1) Elon Musk knows about every detail of the rocket's design. 2) They make almost all the parts in house (literally in the same factory). 3) The work ethic/culture at SpaceX is very high. If something needs to get done, Elon will make sure it gets done fast.
They somehow maintain a high rate of progress despite how huge the undertaking is.
SpaceX is innovating off of NASA's inventions so it has a smaller barrier to clear.
NASA is in charge of space exploration and space science with a budget that can really only handle one. In addition, politicians and not engineers run NASA.
NASA once had the job of putting man on the Moon and bringing them back before 1970. The mission is much broader now, the budgets much smaller and everything seems designed around generating as many jobs in as many places as technically possible (and frequently beyond that boundary). I'm not surprised at all.
