I mean, what are the odds that an already extremely unlikely event would occur in exactly the right way, and in exactly the right time to be leveraged most effectively?
For all of the talk you're doing about how thoughtful you are, you don't really seem to have put that much thought into this. Is this really exactly the right way to be leveraged most effectively? It's not like this even involved guns: if anything, it shows that guns aren't the cause of mass murders. What'd be much more "convenient" (your words, not mine) is if someone who would have failed a background check had shot a bunch of people, or if someone had shot a bunch of innocent people with an assault weapon because they thought they were stopping terrorists, or, you know, literally infinitely many other possible situations.
The most futile thing about all of these "not conspiracy theories," though, is that none of the people positing them have any idea who the bomber is.
He'll be white, right-wing, have a grudge with the government, have a problem with Obama in particular, be pro-second amendment, anti-abortion probably -- You know, basically a caricature of an extremist republican or tea partier.
Oh? You do know who the bomber is? Why didn't you say so?
The truth is that it could be a right-wing extremist, or it could be a left-wing extremist, or a whig extremist. it could be a white person, a black person, a middle eastern person, an asian person, a hispanic person, or someone from Jupiter. But one thing is almost certain: whoever the bomber is, someone out there armed with a conspiracy theory and a poor understanding of probability will have "eerily" predicted who it is, and that person will see that as conclusive evidence that their "suspicion" is justified.