Egos get in the way.
Putting all the information out there in one shot would be what the MSM and Democratics want. The most damming information would be buried by the quantity and the MSM would divided up the attack. It would be out of the news cycle in a four days. Remember the old Chinese water torture? Drip, Drip, Drip. Undecided voters will wait to the last minute to make their decision . A damming piece of information should be the last thing they see before going into the voting booth.