I first read about Vactrains in the Usborne Book of the Future of the seventies, which credited Dr Robert Salter, although the idea goes back a fair bit further.

https://en.m.wikipedia.org/wiki/Vactrain

Elon's idea seems to be to make it quite a bit smaller, and to have the tubes above ground, which does make it more feasible.

Is his association more to do with branding?