Off the rails, yes, but there's a difference between "fuckin' crazy" and "out of character." He's been just as excited and gotten all "ufufu look at my evil grin fighting is so cool" every time a chance to fight something tough has come up, so it's not unexpected that he'd go out of his way to set this situation up. It's not exactly what we would call the most reasonable approach, but it's not at all contrary to what we should expect from him. If he's insane, he didn't go insane out of nowhere, he's been insane the whole time.