1) The antisemites and America-haters, with the “Death to Israel” missiles and “Death to America” threats, was cheating, enabled by the secret side deals and the inability to fully investigate their evil ways.
2) You don’t continue a deal with a proven untrustworthy opponent when they refuse to honor it. Iran is run by an evil government that funds terrorist activities, and Obama was so eager to work with Muslims, to whom he is biased, that he hid the deal from Congress and brought it to the pro-Arab UN to rush through.
3) Maybe if the lefists, led by sore loser Hillary, hadn’t concocted a treasonous accusation such as Russian collusion, and pushed the lie through for years, Trump could have done something, But honestly, any deal would be in name only, since the Iranians would have cheated anyway.