Why did Vedic rituals become increasingly dependent on trained Brahman priests?

During the late Vedic period, rituals became increasingly dependent on trained Brahman priests due to their growing complexity and the strict requirement for precise execution. As these ceremonies evolved, they became governed by innumerable rules and intricate techniques that required specialized knowledge of the Vedas and sacrificial formulas.12

It was believed that the efficacy of these rites—which were thought to influence cosmic processes and maintain the order of the universe—depended entirely on their correct performance. Because improperly or incorrectly performed rituals were feared to bring about disaster or death, the role of the Brahman officiant became essential. Brahmans were viewed as the exclusive custodians of this sacred knowledge, possessing the necessary insight into the correspondences between mundane acts and transcendent reality. Consequently, they established themselves as the indispensable masters of sacrifice, holding supreme control over the fortunes of both gods and humanity.1234