The easiest way is a much earlier oil crisis, which results in greater use of nuclear power. Next mix it with thorium being used. Here we could have the allies banning Japan and Germany from standard nuclear power and instead we see them invest into thorium reactors, as thorium are safer and cheaper, most countries who doesn’t plan to use plutonium for anything (nuclear weapons) decides to go with thorium reactors. As electricity have become dirt cheap and oil prices are high, we also begin to see a increase in artificial manufactured fuel.
Thorium isn't necessarly safer and cheaper. I found out, when getting some documentation about it, that there are tons of different concepts for thorium reactors, all of them with various advantages and issues. Some of them make proliferation even easier than uranium/plutonium reactors, actually, while some of them aren't particularly safe. I don't like to be that guy, but it does annoy me (a little, not that much, though) to see that people have ended up (due to a lack of institutional communication, IMO) mixing all models and concept to imagine a perfect thorium reactor that combines all advantages with no drawback. I'd suggest you to check on "Molten Salt Reactors and Thorium Energy", by Thomas J. Dolan (Elsevier editions) if you want to know a bit more about it. My degrees ain't in nuclear engineering and I found it pretty accessible overall, if long.
Checking it right now, and among the chapters, I see:
Liquid fuel, thermal neutron spectrum reactors
Fast-spectrum, liquid-fueled reactors
Solid fuel, salit-cooled reactors
Static liquid fuel reactors
Accelerator-driven systems
Fusion-fission hybrids
Throium molten salt reactor nuclear energy system
Integral molten salt reactor
ThorCon reactor
Molten salt fast reactor
Stable salt fast reactor
And a few others. Then there are the reviews of work being done often very independently in almost two dozen countries, on various models with a handful of proofs of concept for part of the extremely complex equipment needed to make such reactors work. TL, DR? They aren't a magical solution to the issues of nuclear power generation.