You need to let go of the illusion that there was any actual permanent "deal" in place at all. What was in place was a temporary stopgap at best, and Iran would exit from that stopgap with multiple avenues to building nuclear weapons within a year or two after the expiration of its provisions. If the goal was to prevent Iran from building nuclear weapons, the "deal" didn't accomplish that at all, it merely postponed it. Letting an extremist theocratic regime (and a known sponsor of terrorism) eventually arm itself with nuclear weapons in a powder keg that's the Middle East seems like a terrible deal to me. Much worse deal, in fact, that not doing anything about North Korea for two decades.