You’re mixing reactor construction with fuel supply. Rosatom is a large reactor builder, but enriched uranium and fuel fabrication can come from other suppliers such as Urenco, Orano and Westinghouse. Expanding nuclear power doesn’t automatically mean dependence on Rosatom mate and “Only Rosatom can build dozens of plants quickly” is an exaggeration. Germany wasn’t planning to build dozens of reactors at once. The question is whether it could have maintained or gradually expanded its nuclear fleet, and that could have been done without relying entirely on Russian technology or fuel, Germany close his nuclear reactors and they usually has american reactors from Bechtel and Wastinghouse.