It wasn't pilot error. During shutdown, monorails from EPCOT loop have to be shunted over to the MK loop. During this procedure the emergency stop system has to be overridden or the monorail will auto stop preventing the transfer. The EPCOT train needs to back through the TTC station. During this operation a supervisor is supposed to be onsite visually assuring the beam is switched. It was not and the supervisor was over at Denny's. As train #1 was backing through the station train #2 was approaching. While train #2 could see the approaching train, the operator in train #1 could not.
This wasn't the first serious collision though. Back in the 70s trains were operator in violation of rules (but with permission of management) to have six trains on exterior beam. This required an override of the emergency stop system as the goal was to have your nose into the station before the tail of the other train exited, providing continual movement. One train had bad breaks and when applied, was too close to stop and crashed into the other train. This was a few months before I started and was emphasized to me on my training - everyone was on eggshells and overriding a hold area was an extreme no no. (The trains involved were red and blue. One was totally rebuilt). The driver wasn't killed, but seriously injured with life-changing injuries <the annunciator panel nearly cut him in half>. After that, five trains were max on exterior and overriding the emergency stop was only allowed during track transfer.