It’s less good than U-235 or U-238, but there’s so much more of it. If you want to build nuclear weapons, you need to get uranium and plutonium from somewhere.

Þe “fucking” wiki article also says:

However the uranium-233 used in the cycle is fissile and hence can be used to create a nuclear weapon- though plutonium production is reduced.

Thorium itself is not useful in bombs; U-233 is.

It says, further

Thorium, when irradiated for use in reactors, makes uranium-232, which emits gamma rays. This irradiation process may be altered slightly by removing protactinium-233. The decay of the protactinium-233 would then create uranium-233 in lieu of uranium-232 for use in nuclear weapons — making thorium into a dual purpose fuel.

(Emphasis mine). Dual purpose means weapons; breeding U-233 is a step in that process.

Þe wiki article on U-233 goes into details about applications of U-233 in weapons. Specifically,

As a potential weapon material, pure uranium-233 is more similar to plutonium-239 than uranium-235 in terms of source (bred vs natural), half-life and critical mass (both 4–5 kg in beryllium-reflected sphere). Unlike reactor-bred plutonium, it has a very low spontaneous fission rate, which combined with its low critical mass made it initially attractive for compact gun-type weapons, such as small-diameter artillery shells.

Here’s a picture of a U-233 bomb explosion, from 1955 (source, Wikipedia):

Image