What did Donald Trump do today?

He gave the closest thing to an explanation yet to his hatred for the Iran nuclear deal.

As was widely expected, Trump declared today that the United States would be abrogating the treaty it signed along with France, Germany, Russia, China, the UK, and Iran. Since the other signatory countries have pledged to uphold the treaty, it's not clear what the outcome will be: Iranian hardliners could benefit from Trump's decision, and the country could pull out itself, leaving it with a freer hand to develop nuclear weapons. Alternatively, it could remain within the treaty framework, which would put the United States in the position of imposing economic sanctions on close allies. 

Part of the mystery is that Trump seems unwilling or unable to say why he objected to the treaty, other than that it was a "bad deal." (Trump, who hired a ghostwriter to create his book The Art of the Deal, regards himself as the ultimate dealmaker, evidence be damned.) There are serious arguments to be made either for or against the treaty, but Trump himself has never really articulated any specific problems with it, other than his belief that somehow it wouldn't work.

His actions over the past few days have given hints as to the real motivation, though: hatred of the Obama administration. This morning, just before the announcement, he tweet-ranted at former Secretary of State John Kerry, accusing him of "hurting" the United States. A few days earlier, free-associating during his NRA speech, Trump taunted Kerry for having broken his leg while in office.

It's likely that Kerry was on Trump's mind because he (via staff) apparently ordered a private espionage firm to dig up dirt on the members of the Obama administration who were part of the original negotiations. "The idea was that people acting for Trump would discredit those who were pivotal in selling the deal, making it easier to pull out of it," a source told the Observer, which broke the story. 

The Trump White House has refused to comment on the story, or on whether it has bought private spies to dig into other members of the Obama administration.

Why should I care about this?

• It's bad if a president is making major policy decisions for no reason, or for no reason he can say out loud.

• It's un-American to attack people who served their country in good faith.