We'll need to see the reasoning behind this decision but I would not be surprised if the French builder had to step aside because they are constrained on resources. They spent the last decade regaining knowledge on how to build an NPP and while the situation seems much better now, they are still lacking people to handle multiple projects at the same time. And there are plans for massive renewal of the French NPPs that is using numbers on the higher end of what the builder said they could achieve so starting new projects elsewhere might be stretching it.

One other important element is that you get rid of your kerosene as you use it, reducing your mass and thus your propulsion need. But your battery is still there at the end of the flight.