They also didn't investigate reports of John McClane (of the Die Hard movie fame) tossing a cigarette into the warehouse, backwards while walking away, a few minutes before the explosion... I'm unsatisfied that they didn't entertain my conspiracy theory! /s
If you actually informed yourself properly about this explosion (instead of reading -- I'm going to assume -- conspiracy websites), why the whole thing was sitting there for so long is pretty clear, and is actually briefly covered in the video (6:05): no one in the government nor military felt responsible nor did they want to take responsibility, having a fight using letters instead of recognizing the danger and acting to fix it. As to the source/why no one wanted it back, that's also been covered in the media.
If you actually informed yourself properly about this explosion (instead of reading -- I'm going to assume -- conspiracy websites), why the whole thing was sitting there for so long is pretty clear, and is actually briefly covered in the video (6:05): no one in the government nor military felt responsible nor did they want to take responsibility, having a fight using letters instead of recognizing the danger and acting to fix it. As to the source/why no one wanted it back, that's also been covered in the media.