The decision to shut down the Molten Salt Program within the AEC was driven by Milton Shaw, who also and at the same shut down numerous other programs: sodium graphite program (Hallam), organic program (Piqua), superheat BWR (Bonus, Pathfinder), high temperature gas, etc. He shut these down because he wanted all focus to be on the Fast Breeder Reactor (Clinch River). This was all in 1968.
Uranium-fueled commercial reactors never had anything to do with making plutonium for weapons. Plutonium was made by graphite and heavy water moderated reactors at Hanford and Savannah River.
I have read Weinberg! It's my favorite book. It's interesting that at the end he was more excited about the PIUS PWR than the MSR. Here are my reading notes: https://whatisnuclear.com/weinberg.html