in ch.2 why do the animals succeed in the revolution?

The animals have been preparing to take over the farm, but they get their perfect opportunity when the farmer gets drunk and forgets to feed them. The cows go in and help themselves....... the farmer gets angry and whips them. Anger takes over, and before you know it the animals have taken control/ I don't think it ended up turning out the way they expected, but they succeeded by supporting each other.