This proxy theory is ridiculous. Nobody can give a nuclear device to a terrorist gang and then pretend:"Who done this?". This is designed to put people in a stressed out and agressive disposition. On the other hand Iran is not hiding the fact they are a sponsor to Hizbollah, so they can not, and are not trying to, deny responsibilty of the group actions.
Palestinian man suffers light wounds from rocks thrown by Jewish men in Jerusalem (Haaretz)
from the article: Let them have nukes