Trump has consistently criticized Obama's Iran policy -- the chief accomplishment of which was an internationally negotiated deal reached in 2015 that lifted sanctions in exchange for Iran ratcheting down its nuclear weapons program. The Trump administration reimposed all sanctions in 2018.
But before that deal, Trump routinely asserted that Obama would force a confrontation to boost his domestic prospects.
“There’s a tweet for everything.” He doesn’t care about anything but his own image, no matter how poorly he manages it, and no matter how much damage he causes to anyone else or our country.
We have no reason to believe there was an imminent attack, and every reason to suspect this was a stunt to bolster support and distract from impeachment.
His own top aids are giving mixed reports. This assassination, like a lot of Trump’s most consequential actions, likely wasn’t coordinated across government (he doesn’t have the patience or attention span), leaving the Departments of Defense and State scrambling to pick up the pieces.