I never used to believe in "conspiracy theories" however as I have aged and witnessed how power operates everywhere, not just the US government, I am convinced that while perhaps not a true conspiracy, the people are fed lies based upon the narrative that the power structure wants to spread.
While I do not believe they orchestrated it, I absolutely believe they allowed it to happen because they needed it to happen.
I'm not sure that I would personally go that far, but I am sure that the "powers that be" recognized a golden opportunity to further their own agenda with the full emotional support of the American people when it landed in their lap.
In my mind (and I don't mean to belittle the tragedy) it reminds me of the shooting of the Archduke in Bosnia? that started WW1, ie a single incident that would not have been so significant had it happened in less tense times. Frankly, we're all lucky that it didn't happen during the height of the Cold War or by an easily identified target or the button would have been pushed.