It's not really a distraction, it's just it's own stupid, horrible thing.

The most sane reason for "why now" would be because Iran was in a relatively weak position (domestic unrest, severely weakened proxies due to Israel) and the hawks saw an opening

That and Trump was more easily moved now that he's developed a taste for military shows of force after the Maduro thing. He probably thought it would make great content.

The Iran hawks and Netanyahu probably didn't have to push him very hard