A democracy or not (currently not), it is in Iran's interest to get nuclear weapons. Pakistan, China, India and the USA have nuclear weapons and desperately need cheap oil. Iran has too many neighbours that can't be trusted. Iranians have suffered too much during the never-ending Iran-Iraq war. The population supports nuclearisation of their country. And who can blame them?
If every country in the world used their military to invade the USA, the world coalition would lose. That is how much the USA spends on its military.