I used to think that as well...but how many people would have to be in the cover up? I saw the video...you could see the plume from the missile bouncing up as it was launched, and the rate of vertical acceleration seemed much more powerful than that a shoulder fired missile.
Many autos and light trucks have open-frame fuel pump motors sitting in the gasoline that are perfectly safe because there cannot be enough oxygen to ignite the fuel.
The theory that the center fuel tank exploded due to some electrical malfunction inside the tank is so implausible that it cannot negate the testimony of dozens of credible witnesses who saw some object ascend towards the aircraft before the explosion.