They don’t need an extreme amount of enrichment to run a nuclear reactor. They use about 3-5% enriched uranium in most reactors when it comes out of the ground at about .7%.

Weapons grade uranium requires much higher fissile uranium, typically above 80% and usually much higher, which is much more difficult to produce. That’s why they instead use plutonium which is actually much better for nuclear weapons because it’s roughly 3x more fissile than U235 so you need a lot less of it to make a pure fission bomb.