> What makes you think they will give nuclear weapons to terrorists or use those weapons at all?

The Islamic Regime is effectively a terrorist organization itself, so Iran getting nuclear weapons would be effectively giving a terrorist Jihadist organization a nuclear weapon. The Islamic Regime simply cannot be allowed to obtain a nuclear weapon and the military costs to stop them will continue to get higher as time goes, this is a problem that we will inevitably have to deal with and dealing with it sooner rather than later is likely always going to be the best option as the costs to deal with the Regime will only continue to increase.

> This does not happen even in the most insane examples like North Korea.

North Korean leaders value self preservation much more than the Islamic Regime leaders do, they also do not use terrorism in same way or to the same degree as Iran does. North Korean leaders also don't generally have ideologies similar to Martyrdom/Jihad like Islamic Regime leaders have(these ideologies specifically make traditional mutually assured destruction deterrence strategies largely ineffective).