Given the unpopularity of the war, Trump desperately needs to make a plausible deal on nukes and then get out. This would, in all likelihood, resemble the 2015 Obama deal. Unfortunately for Trump, he has repeatedly described this as a surrender to the Iranians.
So what does he do? He needs something at least slightly better than the Obama deal in order to avoid embarrassment. It is not clear that the Iranians will make him that offer. It is clear, however, that Bibi will be mad as a hornet if it does happen.