Iterative hardware development can take time. A brief search suggests: Using the Prufrock-2 version TBM, the Las Vegas Convention Center loop has picked up a couple of nearby hotels, and work has started on the first long extension, 3 km south along Paradise Rd to near the airport (1-2 years). Prufrock-3 is being exercised tunneling around the Tesla Giga Texas factory[1]. Prufrock-4 is nearing completion, and -5 is in design.
If you want good transit, it must be for the people who vote. Otherwise they will vote to make it bad to save tax money. Branding public transit as the affordable option is a guaranteed recipe for failure.
Transit projects must also be small enough that the entity responsible for them always has several projects running in parallel. Once you stop building, you will quickly lose expertise, and subsequent projects will be more difficult and more expensive.
When there's a will to get it done, it gets done. When her isn't, planning and permitting takes a butt load long time.
> Musk admitted to his biographer Ashlee Vance that Hyperloop was all about trying to get legislators to cancel plans for high-speed rail in California—even though he had no plans to build it.[1]
He knew it would delay CA-HSR and political will for it nearly died.
1. https://time.com/6203815/elon-musk-flaws-billionaire-visions...
https://x.com/parismarx/status/1167410460125097990
Note also that the excerpt in this tweet omits the subsequent page, which discusses how Musk began taking the project more seriously after being surprised by the amount of public interest. You can find the biography on libgen.