The article clearly states we have the tunnel tech. That's not the issue. We already have the tech to connect a lot of American cities with decent trains again. It's about buy-in from the communities, the ability to put up stations (safely, faster, more efficiently) and Americans to stop screaming "our spaces are too far apart." They weren't less than 100 years ago. They will collapse back in once we start building transport again.
As shown in the article, the current tech is really good. It just takes time and the biggest problem are the stations, track and power. These car tubes that Elon is proposing are terrible. We need a faster way to put up full metro systems.
Perhaps it has nothing to do with tech, but framing it as a tech problem lends credibility and allows for easier structural changes/violence. It is easy to say "here's how to improve transportation because xyz is a tech issue" than to say "we have a NIMBY and willpower problem, let's hire some political grads to draft a plan on lobbying politicans and researching the impact of solution abc", especially when your past achievements are all tech related.
Also tech has the perception of being hard, inflexible. Just ask anyone who had to contact Google for customer support. Tech billionaires are not known to be easy to sue either, at least compared to a bunch of city-council bureaucrats. See the first paragraph of this article as an example of how tech CEOs are portrayed in the media versus city government bureaucrats:
https://www.wired.com/2017/05/apple-park-new-silicon-valley-...
Framing it as a people problem is simply asking for interference by third-party interests, which is one of the main factors currently preventing accumulation of sufficient political willpower to build metros. It may be a cheap, unethical hack in the sense that the state avoids having to exhaust political capital/use controversial powers like eminent domain in exchange for having private interests build poorly thought out transportation infrastructure. At the end of the day there is an unfulfilled need for transportation infrastructure. A poorly thought out one is still better than nothing.
As shown in the article, the current tech is really good. It just takes time and the biggest problem are the stations, track and power. These car tubes that Elon is proposing are terrible. We need a faster way to put up full metro systems.