I want to ask a question about Oedipus Rex. It may sound silly or straightforward, but why does it need to happen: kill Oedipus for fearing he is the cause of his father's death, King Laius, for the...

I want to ask a question about Oedipus Rex. It may sound silly or straightforward, but why does it need to happen: kill Oedipus for fearing he is the cause of his father's death, King Laius, for the prophecy not to occur. Wouldn't it be easier if the Gods won't just let it happen? Or is it, prophecies are the Gods' thing in Greek Mythology? Because it only created chaos wherein Oedipus isn't the only people affected in this prophecy but the children of Cadmus, too.