You’re leaving out a key part of the story aren’t you? “Having found out that Mordecai is Jewish, Haman plans to kill not just Mordecai but the entire Jewish minority in the empire.”
Your analogy to what’s happening now is quite apt, though. Iran had peaceful relations with Israel for decades. It was the second Muslim country to recognize Israel. But for decades since then it has been funding terrorism and launching missiles aimed at Israel.
It's fiction.