Final answer:
The Shah lost power in 1979 due to widespread discontent with his oppressive regime, influenced by foreign powers and the uneven wealth distribution from oil revenues, which paved the way for Islamic fundamentalists led by Ayatollah Khomeini to take control.
Step-by-step explanation:
The Shah lost power in 1979 during the Iranian Revolution, a pivotal event that ended the Pahlavi dynasty and established the Islamic Republic of Iran. Shah Mohammad Reza Pahlavi's government was seen as oppressive, corrupt, and heavily influenced by foreign nations, particularly the United States, due to its support for the Shah's rule and investments in Iranian oil. This dissatisfaction with the Shah's regime provided the perfect ground for Islamic fundamentalists, led by Ayatollah Khomeini, to garner support and eventually overthrow the existing government. Islamic fundamentalists played a key role in the revolution by mobilizing the masses and harnessing the general discontent with the Shah's policies which included the modernization and westernization efforts that conflicted with traditional Islamic values.
The United States had helped reinstall the Shah after a joint CIA and MI-6 operation overthrew the democratically elected Prime Minister Mohammad Mossadegh in 1953. This had long-lasting implications, breeding resentment among Iranians who were opposed to foreign intervention and the unequal wealth distribution from oil revenue. The Shah's repressive tactics using his secret police, SAVAK, further fueled the opposition that led to his downfall. His exit from Iran and the storming of the U.S. embassy in Tehran highlighted the extent of opposition against him and solidified the hold of Islamic fundamentalists in the new government, steering the nation toward a theocratic rule that continues to define Iran's political landscape today.