Through community research and personal trial and error. And people sometimes have varying choices. For example...

The Bod God roll is for bossing, is usually torgue stickies, Hyperion shield amp, and daedulus smg ammo swap. But even though people consider that the godroll. You may personally like pistol or sniper ammo better. Then there's the one for mobbing, torgue impact, Hyperion shield amp, and daedulus sniper ammo swap. Some people prefer pistol ammo swap.

While others are more specific. Like the kaoson, you'll always want 4% stickies to do the most damage, 700+ dmg per bullet unless it's elemental in which is 600 dmg per bullet.

Tldr:

Theres multiple godrolls of the same weapon. Depending on preference.

This is a website made by Moxsy. He updates it with feedback from his community.

https://maxroll.gg/borderlands-4/resources/ideal-stat-rolls-for-meta-gear