SpaceX entered a market with few competitors, none of which are defacto government agencies. The civil engineering market is much more competitive. Expecting the same level of cost reduction just by having better operational efficiency is naive.
Thus the argument needs to be that Hyperloop is intrinsically cheaper, whether built by Musk's company or any random civil engineering company. I don't see any reason why that is the case, Hyperloop looks a lot more complicated than HSR to me.
Musk himself didn't expect SpaceX to succeed. It was one launch away from complete failure. You're essentially making the argument "If NASA can put a man on the moon why do I still have to buy toothpaste?"
SpaceX has and continues to do amazing things, that doesn't mean suddenly everything we want is feasible.
Thus the argument needs to be that Hyperloop is intrinsically cheaper, whether built by Musk's company or any random civil engineering company. I don't see any reason why that is the case, Hyperloop looks a lot more complicated than HSR to me.