Actually not entirely true.

He was proposing transportation method similar to how the communication tubes are. Where vacuum would be used to transport capsules with people.

He knew it was bunk, so initially just published that idea and let anyone do it. His actual goal was to kill California’s high speed rail, which he did.

Eventually he purchased Boring company and started building tunnel in Las Vegas and called that (as you called it, subway for cars) a hyper loop and pretend that it was the original idea.