In 2018 Donald Trump Killed a Chance to Reform and Pacify Iran

Back in 2013 a moderate candidate won Iran’s presidential election. That leader proceeded to work a deal that significantly limited Iran’s nuclear development. The United Nations supported that agreement and six major countries signed on, including the United States. The settlement was effective. Inspectors made several site visits and reported the Iranians honored terms of the agreement.

If negotiations in later years produced more improvements, perhaps we would not be dealing today with an aggressive Iran and a war new war in the Middle East,

How was that remarkable breakthrough achieved, and what caused its demise?