The Shah wa basically incompetent. He didn’t have the “stones” to be a Mideast strongman when “troubled times” required it and didn’t have the ability to finesse it. So instead of being feared or admired he ended up being held in contempt. If you read anything definitive about him and his family they remind you of the last Romanovs. Remember he was educated in Europe (Switzerland I think!), many of his family spoke better French then Farsi. Now his grandfather the founder of the dynasty (Note they were upstart nobodies!) was a tough old cavalry commander. He was trained by Russian Imperial Cossack cavalry officers. He would have known how to handle Khomeini!
The Shah was in power from 1941 to 1979. He was briefly removed from power by Mosaddegh, but a coup organized by the US and the UK returned him to power.
Yes, the Shah was not a "strongman," but SAVAK was quite capable of controlling and taking out any political opposition. There was certainly fear among the political opposition. It was the US led by Carter and Vance that warned the Shah not to use force against the political opposition. The Shah followed that "advice" until it was too late. Brzezinski advised the Shah belatedly to unleash SAVAK, but by that time, it was too little, too late. The Shah was hamstrung by conflicting advice from Vance and Brzezinski.
It is only conjecture, but if the Shah had opted to ignore the US and use SAVAK to eliminate the opposition, the Iranian Revolution may never have got off the ground. They could have assassinate Khomeini in France.
During the final days, the Shah used to summon often Ambassador Sullivan in the middle of the night seeking counsel on what to do. The conflicting advice out of Washington made things much worse. And the treatment of the Shah after he left Iran by the US was a disgrace. It was just another example of the US abandoning an ally when it became expedient to do so. It happened in Vietnam and Egypt and to some extent in Libya. Protecting American national interests should be the primary goal of our foreign policy, not some ambiguous human rights campaign that is directed against our allies.
Iran is far worse off today than it was under the Shah. And we are living with the world's biggest sponsor of terrorism and future nuclear power because of bad decisions by Carter and his foreign policy team.