Charles VI of France was insane. He nearly killed his brother Louis months before this bizarre occurence during the first of his fits of madness, then in early 1393 nearly burned to death at a party where he was covered in wax.
Let's say he does kill his brother, then during a sane moment retains the crown but is injured more severely as a result of butterlies - people are a little more hesitant to step in to save him because of worries he is simply acting insane till they realize, "Hey, wait, the King of France is actually onfire here." So, they stop, drop, and roll him, and his injuries are more severe, but not enough to kill him; he is, however, rendered unable to have children.
So, he lingers for months, and he finally dies, it's 1395 and Louis is negotiating for marriage to Yolande of Aragon; not only will Louis II of Naples now hold France in personal union (and if it's like later with the Hapsburgs in Spain my guess is he'll keep it) but also if he marries Yolande, there's a chance he will be able to claim Aragon through his wife.
So, does he marry her? Does Richard II of England marry her, with Louis (now Louis XI) marry Charles VI's daughter Isabeau, with the idea of further uniting the crowns? (Though she was pretty young then, he would also think of it as a way to help keep Richard from having further claim on France.