In ruling by Dharma, the king was expected to protect the people of his kingdom, uphold social stability, and administer justice. Earthly laws therefore reflect the divine order.
Brahmins of course served the king in administering the rituals that ensured the kingdom’s auspiciousness, just as they performed such rituals for smaller rulers and families.
Brahmins were thus important for ritually or religiously validating the authority of kings. This meant that royalty depended on Brahmins to substantiate their power.
Ultimately, with the rise of Jainism and Buddhism at the end of the Vedic era (6th century BCE), the Brahmins’ authority was challenged