>a more rational world would have gone full steam ahead on nuclear power

Nuclear is not perfect, it has some drawbacks that totally justify not going "full steam ahead". Even if it is the cleanest energy possible and 100% safe guaranteed, it is also very concentrated (at least for now) that makes a plant shutting down for repairment/manteinance a problem, it is expensive to build, it takes forever to increase capacity, it creates dangerous residues, it is not very modulable.

> and have injured the environment to a dramatically greater degree relative to a pro-nuclear alternative timeline.

France is having a problem to install green energy, because their nuclear capacity is so big. The alternative pro-nuclear timeline might be using fossils as the modulable part forever by blocking solar and wind installations.

>and as a result we are all poorer

How? Nuclear is safe, but it is expensive. And it almost naturally lead to monopolies and oligopolies due to their size and complexity, allowing owners to have pricing power. In fact, the economics of building a nuclear plant don't work unless a state subsidizes (i.e. extra costs you won't find in the utility bill, but hidding in your taxes, ask the french) its build and insurance costs.