I think this is mostly due to the fact that the advantage of nuclear is long term and humans -- and especially politicians and bureaucrats -- aren't good at long term planning. Globally we basically rolled out a bunch of nuclear plants and went "welp, that'll hold us off for the next 50-60 years." It's like exercising and eating right for a year and expecting this to keep you healthy for decades as you eat poorly with little to no exercise. Maintenance and continual production is key to cost reduction and advancement but this is something nuclear never got. I really do think nuclear's biggest flaw is its lifespan. Just allows people to get lazy.