In 2015 P5+1 signed an agreement(JCPOA) with the Islamic Republic of Iran and after 3 years, Trump revoked the deal and now they are about to revive it. Given that the deal does not have enough support in the Congress and considering strong opposition in the region(Arabs and Israel), what's the interest of reviving it when it will probably be annulled after two or six years?
Politics is a matter of long-term pressures, not short-term actions. The point of passing a bill like this is to establish a principle and create some institutions, because principles and institutions are difficult to uproot once they take hold. Trump was unique to the extent that he had no regard for institutions, political consequences, or precedents; no other president would have taken that kind of abrupt unilateral action. Barring the unlikely event of Trump's re-election, the agreement should stand.
In normal US contexts, short-term political grandstanding belies long-term political stability. Lots of political leaders are willing to take a verbal stand against this or that, but are generally more cautious about actual behavior. The question is whether we are returning to something resembling a normal political context, or whether Trumpism will regain enough political standing to reassert its Pyrrhic quest for power.
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 export gas to EU as can be seen in this article and EU needs that gas, but the main problem preventing it to hapen are US sanctions on Iran.