Those two passengers who missed the flight sound like people who would be fumbling around in the overhead bin causing a delay in the "cabin secure" call from the flight attendants which would have taken an extra 10 seconds to complete the before takeoff checklist which in turn would have resulted in the crew telling ATC to "standby we need to finish a checklist" before accepting the takeoff clearance which would have caused a two minute delay as they waited for the Delta A320 on short final to land an clear the runway which would have resulted in them missing the C152.
Unfortunately after missing the C152 that two minute delay placed them right in the path of an 87 year old who was 13 years out of his medical and was single piloting a King Air and who mistakenly made his downwind to the wrong airport thus collided with the 737 and everyone died.