I don't understand why these same issues get raised every time hyperloop comes up. Of course the engineers working on this are aware of the most obvious concer

I don't understand why these same issues get raised every time hyperloop comes up. Of course the engineers working on this are aware of the most obvious concerns and of course there are solutions. Vacuum collapse is handled with exploding gates along the track. If the vacuum ahead fails, you blow open the gates behind you to even out the pressure and you come to a stop. Track expansion seems extremely solvable with sliding joints and decent seals. Hyperloop is predicated on not being perfect vacuum so slightly leaky seals don't matter. I think Hyperloop is not economically viable because "trains are too expensive" is not solved by making trains way more complicated. But technically it seems feasible.