your favorite characters are nowhere to be found but that's not cause they're dead, the game just forgot
elaboration:
the universe is threatened by an infinite cosmic force who can subvert emotions and can see the future. after a long and grueling battle where many warriors die glorious deaths at the hands of an eldritch horror, some guy runs in and is like "HEY GUYS I JUST REMEMBERED I HAD THIS NUKE" and physically throws the normal, conventional nuclear bomb at space-oracle-cthulu and space-oracle-cthulu is like 'I FORESAW THIS' and explodes
nuke guy and his friends non-native-american-tomahawk man and my-name-is-literally-helmet dude all high five and go for drinks. later, they make friends with silent bob, a miner, the alternate dimensional equivalent of my-name-is-literally-helmet dude and the Angriest Volleyball Player in the World (and a bunch of other unimportant people) and get in a fight with
another space-oracle-cthulu, who is dispatched in exactly the same way
nuke guy (who is now everyone's favorite character) is straight up not a part of the third game because like 90% of the writers are all super mad that 10% of the writers forgetin love nuke guy and nuke guy is canonically the single most useful entity in the universe. there is literally no explanation for nuke guy's absence beyond 'he's here somewhere' and it turns out he's basically just standing a foot or two off-camera at all times