They are radical groups who identify with the violent jihad of Islamacist terror organizations like al-Qaeda, Hizbollah, Islamic Jihad and Hamas. And they have the support of a radical culture that regards America as the Great Satan, and Muslims and Arabs as the people whom America oppresses.
"On the matter of political relations with Iran, the sheikh was absolutely clear. Hizbollah regards the Iranian supreme leader, in this case Ayatollah Ali Khamenei, as its ultimate authority; all major political decisions regarding Hizbollah are referred to – when not actually taken in – Iran. He gave the example of the decision taken in 1992 to enter Lebanese national politics: Hizbollah set up a commission, which prepared a report, with various options; this report was sent to Iran; it was Ayatollah Khamenei himself who took the final decision, in favour of participation."