The trim tab, correctly set, reduces the force needed to move the elevator. This is adjusted in flight to “trim out” stick loads at different speeds. Even in the Austers I used to fly, an incorrectly trimmed aircraft could be almost impossible to control, so in an aircraft travelling at 400 to 500 mph, I would surmise that elevator control would have been impossible. The results would have been inevitable. I’m sure the accident investigation team will be very interested in the missing trim tab photos.
Very sad that such a minor component could cause such a terrible loss of life and injury.