I don’t think it is (only) corruption. I blame two things, on one side there is no meaningful and certainly no long term political support for high speed rail infrastructure, neither in politics nor among voters on the other side legislation is seriously anti-rail development. Laws are tough on any infrastructure projects, causing overheads larger than the actual construction costs (possibly even multifold larger) but they are especially hostile against rail projects and even against operating rail.

Geography isn’t even part of that equation, it is an entirely different debate. (California is not so different from Spain, dry, mix of mountains and flats etc)