Basically when Gandhi was first introduced, he had a major bug. His AI was set to 0 Nuke, or as low as the engine could possibly go, don't know the detail.

Well due to other factors it resulted in his AI dropping bellow 0 to -1. And as you may or may not know, -1 in most programming means infinite. Meaning Pre-Uranium Gandhi behaved like he should. But the second he got the resource his AI had infinite desire to both produce and use nukes. And I mean more than a player at lvl 10 Nuke Propensity.

So Gandhi's Nuke Happiness became famous because he'd randomly declare wars just to satisfy his desire to launch the massive arsenal he couldn't stop himself from building just so he could make more... to launch.

This bug became a 'feature' in later games, as it made the CIV game stuff low key famous. And Civ Gandhi is basically "A nuke for a nuke will make the world mine!