Although Buddhism and to to a lesser extent Jainism had expanded across India during the centuries following the Buddha and Mahāvīra, brahmanical practices recognizing the primacy of the Vedas, and more generally faith in various gods, continued alongside them.
The more theistic philosophical traditions (such as early Vedānta), grew into early Hinduism, in which discussion of Brahman and ātman became talk about the importance of faith (bhakti) in God as the means to attain salvation from saṃsāra.
For instance, the dialogue between the god Kṛṣṇa and the warrior Arjuna in the epic Mahābhārata touch on many of the themes we have already seen in the orthodox and heterodox schools, such as dharma, karma, rebirth, and so forth.