It is a bit sad though for the author. The author never intended the paper to be public. Now he joins the infamous list of people who published to prove P!=NP or otherwise.
And whomever leaked that is going to end up on the shitlist of an entire community of researchers.
But who know what the authors thinking was? Perhaps he hoped they'd share the paper only if they were sure it was right, perhaps he expected they wouldn't share it at all. Perhaps he expected they'd share it and he was already convinced the paper was correct. Perhaps he didn't care to what people outside the field thought...