Right, but the train is making multiple stops. People like to talk about the total length of the line, and some people will certainly ride from terminus to term

Right, but the train is making multiple stops. People like to talk about the total length of the line, and some people will certainly ride from terminus to terminus, but the vast majority of riders will be traveling much shorter distances that are much more competitive with flying. Around the world the mode share split between flying and high speed rail has been around 50% when the rail trip is four hours, and there are plenty of segments on this line that are shorter than four hours.