you are right. Being illiterate doesn't mean their vote can not be counted. But the fact the nearly half were illiterate gives us the reason to believe the a lot of them had absolutely no clue what they were stepping into. In 1930 and 1932 the people of Germany voted to National...
In 1979 more than half of the people of Iran were illiterate. The constitutional monarchy was also approved by the people of Iran, nearly 50 years before the Islamic revolution. Khomeini himself said:
اگر پدران ما انتخاب كردن كه مثلا نظام شاهي بر سر كار باشه حقي ندارند تعيين كننده براي آينده...