That's because he made sure to point it out near the beginning.
He reminded the American politicians in the room, not to mention the Israeli audience back home about to vote in an election in two weeks, that his long-anticipated address coincided with the festival of Purim.
That's the two-day holiday where Jews celebrate the story of Esther — the biblical hero who learned of a plot by the Persian viceroy Haman to exterminate the Jewish people and averted it by warning an oblivious king.
What followed was a modern version — in which Netanyahu was cast in the role of protector, the threat still came from Persia, and the unwitting king in need of a wake-up call was Barack Obama, the U.S. president believed to be on the verge of a historic nuclear deal with Iran.
"The plot was foiled (then). Our people were saved," Netanyahu explained Tuesday. "Today the Jewish people face another attempt by yet another Persian potentate to destroy us."
The symbolism would have been so obvious to an Israeli that a Jerusalem Post article on Tuesday morning predicted the speech would resemble "Purim on the Potomac."
Some secular symbolism in the speech would have been more familiar to a U.S. audience — namely the parallels Netanyahu drew with the Second World War.
He looked up to the gallery and applauded Holocaust survivor and Nobel Prize winner Elie Wiesel. Netanyahu lamented that some modern politicians might have failed to learn from the error of trying to appease Hitler.
"I can only urge the leaders of the world not to repeat the mistakes of the past."
Netanyahu drew repeated standing ovations — more from Republicans than Democrats — in a speech that had three main components:
—He condemned details he's heard about a possible nuclear deal with Iran. He said it would leave Iran with too many centrifuges and he denounced the supposed 10-year expiry date.
—He pushed Americans to negotiate harder — and leave the table if necessary. "Call their bluff. They'll be back, because they need the deal a lot more than you do."
—And he appeared to hint at a willingness to act alone against Iran. "As prime minister of Israel, I can promise you one more thing: Even if Israel has to stand alone, Israel will stand."
One American commentator on the Middle East suggested a political calculus behind the religious messaging.
"This was a campaign stop, 6,000 miles away from the nearest Israeli voter," said Atlantic writer Jeffrey Goldberg, commenting on MSNBC.
"To come to Congress and stand up for the Jewish people and invoke Purim and Haman and Moses and Elie Wiesel in one speech is very powerful to a conservative-leaning Israeli voter and this will probably be very effective."
Many Democrats were less enamoured.
Dozens boycotted the speech, which some called a political stunt. Leading Democrat Nancy Pelosi was there and said she had tears in her eyes, saddened by the condescending suggestion that America didn't recognize the Iranian threat.
Obama didn't meet the Israeli leader. And he was on the phone during the speech, discussing Ukraine with other world leaders. But he said he read a transcript later and didn't sound impressed.
The president said nobody wants Iran obtaining the bomb. And that would be the point of a deal, he said, arguing that the status quo would be far more dangerous than working together to achieve a good agreement.
He said he read nothing new in Netanyahu's speech — with no constructive suggestions. And he didn't mention the biblical undertones.
"I'm not focused on the theatre of it," Obama said.