the agreement is not worth the paper it's signed on. the iranians will break it at the soonest opportunity.
but, trump is being driven by the mental illness of faith in a positive outcome. he wants peace and won't allow facts or evidence to alter his desires. he never does, which is his general problem - he's not empirical. he operates on magical thinking.
trump may end up signing something because he insists on imagining peace as a realistic outcome and won't allow evidence to disrupt his vision, but there is no possibility that this process is going to lead to any kind of substantive peace, and it is merely necessitating a vicious american response in the very near future, perhaps even by the next democrat in the oval office, who might have to go in there and chop some heads off to clean up this mess.
expect this process to lead to nothing other than iranian terrorist attacks, dead americans, more war and an eventual resolve for regime change in tehran in washington. and expect donald trump to be portrayed as a delusional, insane buffoon by historians.