Why did the April 1979 referendum support declaring Iran an Islamic republic?

The April 1979 referendum resulted in overwhelming support for an Islamic republic largely due to the widespread influence and populist appeal of Ayatollah Ruhollah Khomeini.12

During the 1970s, many Iranians—particularly the working poor and migrants from the countryside—became disenchanted with the rapid, uneven modernization and perceived cultural vacuum created by the Shah’s regime. As political repression increased and secular opposition groups were marginalized, these segments of the population turned to the ulama (religious scholars) for guidance. Khomeini, who had been in exile, became a central figure of opposition by framing the Shah’s policies as irreligious and subservient to foreign powers.3

Upon his return to Iran, Khomeini gained broad support as the guardian of the revolution. The establishment of the Islamic republic was rooted in his vision of velāyat-e faqīh (governance of the jurist), which proposed that a qualified expert in Islamic law should oversee the nation's governance. This vision resonated with a populace seeking an alternative to the Pahlavi monarchy's Western-aligned policies.213