Why Buddhism died in India

Gautama Buddha was born a Vedic Brahamin. He was from the highest caste and of royal lineage. He renounced his wordly life and attained Nirvana or Buddhahood. Buddhism initially spread in India and became a state religion. From India Buddhism spread to distant lands like China, Tibet and South East Asia. As the religion spread it slowly died away in India. This is certainly food for thought and one wonders how Buddhism completely vanished from the face of India. There are many reasons for this, but I suppose the main reason is that Buddhism had nothing special to offer. It merely restated Hindu concepts in a different language. In addition Hinduism recognized Buddha as the 9th Avatar of Vishnu and incorperated him in the Hindu religion itself. Thus Buddhism vanished from India but thrived in distant lands. But again Buddhism is not anything unique as far as India is concerned.