Why is Buddhism considered a heterodox school of Hinduism?

Buddhism is considered a heterodox school of Hinduism because it diverges significantly from key Hindu beliefs, particularly in its rejection of the authority of the Vedas, the Caste System, and the concept of an eternal soul (Atman). Instead, Buddhism emphasizes the Four Noble Truths and the Eightfold Path as a means to attain enlightenment (Nirvana) and views suffering as a fundamental aspect of existence. While it originated in the same cultural and philosophical milieu as Hinduism, its core teachings and practices set it apart, leading to its classification as a separate tradition.