I can't find the interview where she speaks in depth about Iran, it was important for the novel because it was a situation where women experienced going from modern equality to having absolutely no rights.

In this interview she briefly mentions Ayatollah Khomeini (the leader of the Iranian Revolution that created a theocracy and removed women's rights), but she's going over dozens of newspaper clippings of other events that inspired the story.

https://www.penguin.co.uk/discover/articles/margaret-atwood-handmaids-tale-testaments-real-life-inspiration