From Wikipedia:

A referendum to dissolve parliament and give the prime minister power to make law was submitted to voters, and it passed with 99 per cent approval, 2,043,300 votes to 1300 votes against.[83] According to historian Mark Gasiorowski, "There were separate polling stations for yes and no votes, producing sharp criticism of Mosaddeq" and that the "controversial referendum...gave the CIA's precoup propaganda campaign to show up Mosaddeq as an anti-democratic dictator an easy target".[84]

A person has to be very gullible to believe 99% of the vote went one way in a fair election involving 2+ million people.