Ezra eyes go wide again as Master Kenobi goes gets to his feet, and he starts shaking his head, because he has serious doubts that that call won't end horribly, somehow. He barely even registers the question aimed at him. He's far more worried about screwing up the galaxy then himself.

Did he do this backwards after all?

It really is the two big pieces of information together that expose the trap, isn't it? So he blurts out, rapid fire, "It's Palpatine. He declared the war over, himself Emperor and the Jedi traitors who didn't want to stand down and tried to assassinate him, all at once. And that makes the troopers just following orders from the highest authority, right? To a lot of people who don't really know them, or the Jedi, it would all make a kind of sense."