Trump has been a special kind of stupid regarding Iran--the kind of stupid a person would be if that person were to treat Fox News as gospel, or believe tabloid journos over intelligence experts. I've tried to plumb where Trump's mindset is with regards to Iran. I can tell you where my thinking has been--I think the nuclear deal was great and had some reverberating effects diplomatically, and that Trump is stupid because he doesn't understand why "Trust but verify, then renegotiate in ten years or so multilaterally" was a better cure for any alleged Iranian nuclear pretentions than "Let them do whatever without any promises with respects to inspections, while also piling on sanctions that made a conflict inevitable."
Trump's understanding of the US relationship with Iran is basically poor. He somehow, ludicrously, believes that Iran came out better in the deal, and that releasing to Iran their own long-withheld funds is a kind of gift. He thinks confiscated Iranian assets are a gift to Iran. They are gifted with their own money.
So stated like a multiply-bankrupt con artist. How outstanding.
But what does a weakening of the Iran deal do for Trump's hand elsewhere--like North Korea?
Oh, it is weakened, because now foreign deal makers realize the US word is not worth as much as it used to be. Because a faithless man is in charge.