how were the pigs able to persuade the other animals that they should get all the milk and apples, instead of sharing them equally amongst all the animals

The pigs claim that they need milk and apples in order to power their “brainwork.” Squealer says that, were the pigs to stop eating milk and apples, they could lose their powers of organization and Mr. Jones could come back. The threat of Mr. Jones’s return is enough to quell the other animals’ doubts and questions.