There's no evidence that TWA 800 was struck by lightning or that any kind of equipment failure occurred on the flight that night. But there's a lot of evidence that TWA 800 was struck by a missile. The NY Times initially reported that the FBI found residue from explosives on the plane wreckage. Later they followed the Clinton party line and switched to the exploding fuel tank theory. If you want to believe the official conclusions and the CIA's rediculous animation of the crash then go right ahead. You have the right to ignore any evidence you want to ignore. But I wouldn't dismiss Cashill and other highly competent people who doubt the official conclusions too quickly. You can start by reading some of the threads about TWA 800 here at FR.
If you believe the NTSB report concerning TWA 800 is a government lie produced to cover up a crime, you are by definition a conspiracy theorist. You may be right (obviously I don't believe you are), but you are a conspiracy theorist nonetheless.
"My point it that aircraft fuel vapor is not explosive under normal operating conditions of commericial aircraft."
I think it would be more accurate to say it is always explosive, it just doesn't explode under normal operating conditions due to carefully engineered systems designed to isolate it from sources of ignition. But obviously, based on a long history of fuel vapor explosions, those systems sometimes fail.
"There's no evidence that TWA 800 was struck by lightning or that any kind of equipment failure occurred on the flight that night."
It is true the TWA 800 was not struck by lightening. However, it is untrue to say there was no equipment failure on the flight that night. The fuel quantity indicator system was experiencing a series of electrical surges that was causing inaccurate fuel readings in the cockpit. One of the last comments recorded on the cockpit voice recorder (about one minute before the aircraft explodes) is from Captain. He says, "Look at that crazy fuel flow indicator on number four." It was short circuiting in that system that is attributed to producing the spark inducing excess voltage in the center wing tank.
"But there's a lot of evidence that TWA 800 was struck by a missile."
The irony of that statement is there is NO evidence TWA 800 was struck by a missile. ALPA, Boeing, TWA and the NTSB all agree on that point. You listen to paid conspiracy theorists like Cashill for your information. I'll stick with the true experts.