Perhaps you'll be shocked to hear that countries like Sweden have HSR despite not being particularly densely populated? It's absurd how much money is poured into roads and yet never attracts the same criticism.

The areas in Sweden with railroads are more populated than the Van/Sea/Pdx corridor, by about 1.8x, more if you drop a couple outlying small towns that don't make sense in themselves to connect except for network completeness reasons. Also, railways in Sweden are more middle-speed trains these days, running 200km/h as far as I am aware. These people are proposing 300km/h+ which requires a significantly higher level of track investment - you can't just use standard sleepers and bolted rails.