there are a zillion stories that can be told on that. let's face it. Michael making an appearance in front of people meant a force like an atomic bomb going off. people just lost it. there were a lot of really bright camera flashes(Michael trying to cover his eyes, even with sunglasses on), the crowd was up against the bus, practically..it must have looked, to Michael, like a bomb went off in front of him..IMO
people thought that because Michael was this genius mythic like dancer and being, that it was not possible for him to fall down, like an ordinary human being. i remember the 'Remember The Time' appearance with Patti labelle..he said his ankle was ailing. the audience didn't believe him. it was like he wasn't a human being to them. that was the curse of his great talent.
in this bus scene, it's possible he couldn't see in front of him, because of the pandemonium so close up. and it's possible that that is why he fell. of course, people can speculate the other stuff too. one thing i notice, is that humanity..we are in love with telling stories, to get attention, even if they're not true. it's sorta like a disease, especially with the advent of tv talk shows. i wonder if, since a lot of people contradict each other with the stories they tell in those interviews in that vid, if many of them just wanted a moment in the spotlight, and would say anything to get it, even if it wasn't true. after all, they knew the world would be watching, because Michael Jackson was the subject.