It all started in 1953 when the CIA orchestrated a coup that deposed the elected PM of Iran and replaced him with the Shah, whom the US was friendly with. In 1979, the Shah was overthrown in a revolution that made the Ayatollah leader thus, converting Iran into in Islamic state.
The Iran PM the CIA outsted was a beloved figure in Iran. During his tenure, he was said to have introduced positive social and economic policies, the most significant being the nationalization of the Iranian oil industry. Now the UK had controlled Iran's oil for decades
Since the PM was dead set on nationalization of the Iranian oil assets, the UK had no choice than to ask America for help which led to the overthrow of the Iranian PM and was replaced by the last Shah who would effectively maintain Iran as a client state for the UK and the US.
He ruled for 25 years before being overthrown. He was seen as a puppet of the west and heartless by his people. The US and UK turned a blind eye to all his evils because he allowed them unfettered access to the oil.
When his government crumbled, the Shah escaped to America as a political fugitive and Iran has never forgiven America ever since. Their main offence was not letting the west take all of their resources.
