Hyperloop is a mediocre (well, actually bad) idea. It indicates that Elon is not some genius level engineer.
I think you underestimate the degree to which luck plays a role in the development of companies.
I think you underestimate the degree to which luck plays a role in the development of companies.
High vacuums are expencive to maintain and take longer to achieve after a leak, but would allow for faster speeds. They also force maglev or something like it to achieve those speeds which is expensive. It also forces you to carry an indecent air supply, and cooling becomes a significant issue.
At STP you just have a normal train which is limited to a few hundred miles an hour.
Between those extremes you need to deal with some air but you can compress it for passengers. Further, you can quickly pump down the air pressure using fewer pumps. You can fly / use ground effect avoiding the mag lev issues.
Heat is really the largest issue, compressing air heats it as does friction, and your passengers / equipment also generate heat. So, you would want the air kept at very low temperates.
Why not just use nag lev? You get faster speeds and as strange as it sounds lower cost per mile of track.
TLDR; Lots of useful trade offs.