Animal Farm- why does the rebellion happen?

The animals rebelled because:

1. Mr. Jones was becoming a bad owner, drinking his earnings away and forgetting to feed the animals.

2. Old Major, the prize boar on the farm, urged the animals to envision a better world where animals govern and that is how they should be treated, not giving all the fruit of their labor to humans.

Then the animals rebelled to achieve Old Major's dream. The song Beasts of England was the animals motivational song for rebellion.