Nuclear power, but that’s largely because it threatened an industry so powerful it literally defines the geopolitical order and is the entire basis of multiple world economies (fossil fuels). That’s what it took and the slowdown really wasn’t that profound, a couple decades maybe.

It was also possible to slow down nuclear because it’s so capital intensive. A gaming desktop or very high end laptop is enough to do meaningful work on AI, and to get to scale requires a tiny fraction of the cost of even thinking about breaking ground on anything nuclear.

Never if money could be made.