It's the President's Bday. And the Q+ = Q just landed check. Catching an attempted assassination attempt in the act is definitive proof of treason. The entire communication thread from that phone is physical evidence they can use in court, not just rely on sigint that might have issues being released. Better public presentation also.
"X was found with a gun while driving for the res pool. Upon routine inspection of his phone, we found…" Shows intent, motive and conspirators.
as opposed to:
"We were monitoring Y and heard the call for X. We notified USSS and they stopped him ahead of time"