Between Rubio's video message, Trump's Oval Office comments, and the planned address tomorrow night, my guess is the admin is finally buckling to pressure (likely from the rest of GOP and in response to polling) to clearly frame why this war was necessary, why it had to happen now, and how they plan to end it.
Going off what we've seen so far, the message is: Iran was trying to build a "shield" of missiles and drones, behind which it planned to rebuild its nuclear program in secret. The US had to go ti war now before Iran got too far along toward building a bomb.
That's the pitch, as far as I can tell.