It's too costly to build high speed rail in many parts of the world (California for instance). It's not because high speed rail isn't a viable solution, it's regulation.

The article you posted from sciencedirect supports this. The study points primarily to a changing complex regulation landscape as a primary driver of costs. Meanwhile, France is in an excellent position in the EU in terms of energy in large part because it stuck with nuclear instead of attempting unsuccessfully to transfer to wind and solar like some of it's neighbors (who now burn lignite to meet energy demands).

Solar panels, for instance, are mostly made in places where actual costs of construction are externalized to the environment and workers with depressed wages. Nuclear plants need to be built and decommissioned in the same place - places that are often actively hostile with complex regulation meant to curtail nuclear specifically for the sake of non-proliferation. SMRs help sidestep a portion of this hostile regulation but there are countless reactor designs that are possible that we can't even begin to explore until regulation is made reasonable.