The Iranians should have been more cautious of his security, whether the danger came from the US or ISIS or anyone else who might try to kill him. Iran was overextended in places where they lacked control of the airspace, but also perhaps they underestimated Trump.

Trump does not need to adhere too closely to the norms of international relations, since his main objective at this point is to get re-elected, and the American public would rather have a tough guy who throws America's considerable weight about on the world stage. On some level Americans will always hate Iranians, even more so than they hate Chinese, because they feel the Iranians betrayed them by overthrowing the US-supported Shah. So to escalate things versus Iran can only help Trump politically.

BTW those media sources may or may not be reliable, since they are as biased against Trump as they are against China.