The main interest of the West is to get more oil and gas, both of which Iran has. In the context of the current conflict between Russia and the West, the West is trying to get these goods even from countries which are not known to be friends of the West, like Venezuela and Iran. The reviving of the nuclear deal will give the western companies the possibility to do business with Iran again, including buying oil and gas.
Iran is willing to exporexport gas to EU as can be seen in this article and EU needs that gas, but the main problem preventing it to hapendhapen are US sanctions on Iran.