User blog comment:The dark lord of fire/hades/@comment-3146930-20111212014536/@comment-4640327-20111212233229

If Zeus didn't command the rebellion the gods would divide between Hades and Zeus. They were fewer, just five against the Titans. If they fought they wouldn't stand a chance, so that is the reason why he agreed. Their best chance was sticking together and deciding stuff like that if everything worked out. Also, they knew it wasn't over after they sent the Titans away so there was no point in fighting and making things more unstable than they were. Better to keep the underworld by yourself, than Tartarus with all his brothers.

And if you say they drew lots, why was Hades cheated?