The cable networks were pushing this line pretty hard on Thursday. His decisions, namely getting out of the Iran deal, led to this precarious situation. It seemed like they were trying to make the case without drawing attention to any specifics about the Iran deal. So since you are doing this, too, what exactly is your reasoning? i.e. did you think the Iran deal was any good? Why?
So, Iran is actually a democracy even though we don't like to admit that here in the US. Like any democracy they have extremists and moderates vying for power. They haven't been in a war since the Iraq Iran war decades ago. There are factions in the Iranian government that might be happy with a war but there are factions that just want normalized relations.
The Iran deal wasn't particularly strong but it did bolster the non-aggressive factions in their government. They were able to go back to their people and say, "see? The West can be worked with. We can now rebuild our economy."
The deal was working, their weapons program was slowed, it didn't actually cost the U.S. money. The money they got from the deal was assets we seized years ago. It bolstered the democratic (little d) side of their government and undermined the more theocratic hawkish side.
Now Trump tears up the deal. Their weapons development isn't throttled at all. The more fascistic factions in the government can now say "see, we were right, you can't trust any deal of treaty made with the U.S. Make sure we're in power so we can protect you." We now have bases, ships, troops etc surrounding their country skirting so close to their airspace that it's apparently hard to tell whether we're violating it or not. Trump's actions have led to this brinksmanship. Trying to take credit for avoiding a situation he's built up is pretty absurd.
This reminds me of what a lot of Trump voters said about Clinton. We made a deal with Gaddafi, he stepped down from his place in the African Union and gave up weapons, then Hillary apparently played a hand in orchestrating his death. After seeing that why on earth should NK give up their weapons? Trump voters said that in a lot of conversations on why she was bad. It was the truth.
The deal was made. Doesn't matter what we think about it retroactively. Tearing it up makes a pact with the U.S. as fickle as our elections. It doesn't matter if some people think it was weak, it was better than what we have now. What we have now is a situation where we're very likely to waste trillions and thousands upon thousands of lives on another war that even if we win won't benefit the American people and won't make them one iota safer.