Maybe because it is not necessarily the incident but the cover-up that leaves many with distrust.
Same doubts exist on the Oklahoma/Murrah bombing, the Branch Davidians, the Ron Brown autopsy, the sense of cover-up feeds the conspiracy stench.
There are also a number of people that think the Earth is flat. Read the report and pay particualr attention to the experiments. They did a great job of recreating the incidents. The only thing about it was the sequence of events that led up to the explosion. There was a long chain of events that had just one not happened there would have been no explosion. It was a classic example of bad luck. The main culprit was the short in the wiring bundle outside of the fuel tank. That is what killed them.