“If a pass is caught simultaneously..”
si·mul·ta·ne·ous Show Spelled[sahy-muhl-tey-nee-uhs, sim-uhl-] Show IPA adjective existing, occurring, or operating at the same time; concurrent: simultaneous movements; simultaneous translation.
The ball clearly was NOT caught at the same time. Once caught, the catcher must retain control until he comes down - the defender did so, regardless of Tate coming in AFTER the catch (not simultaneously, or at the same time) and getting his hands on the ball. Establishing contact after the catch does not constitute simultaneous possession.
There was no catch until both feet were on the ground. Tate had both feet on the ground and was touching the ball. Jennings did not have both feet on the ground before Tate touched the ball. All you need to do is have a hand on the ball which was what the officials saw and ruled it a touchdown.