It was a horrific tragedy, there's a good documentary on the attack if anyone is interested.
We can only really speculate of the Jews' reasons, as there is no official reasoning I know of from them that isn't just the Israeli government excusing it with "well, it was all just a big accident". It could have been some sort of failed false-flag-style operation (it wouldn't be the first time, with the Lavon Affair a decade-and-some earlier), or maybe some matter like what anglo_bvll said, but we really don't have a definitive answer.