John the Fearless, then just John of Valois, heir to the duchy of Burgundy, was one of the leaders of the French forces sent to aid King Sigismund of Hungary in his war/crusade against the Ottoman Turks in 1396. OTL, the Battle of Nicopolis (25 September 1396) earned him the moniker "the Fearless", though the battle itself ended badly for the crusading forces. John was captured by the Turk, and later ransomed for a princely sum.
What if instead of merely being captured, John of Valois had been killed on the battlefield? His future heir, Philip (later "the Good"), had just been born around the time he left for Hungary, but the reign of one of the most important rulers of Valois-Burgundy being cut short years before it even begun OTL would surely carry with it consequences for Burgundy, France, the Hundred Years War and western Europe as a whole.
Assuming Philip the Bold dies roughly according to schedule, this would leave his 8 year old grandson as the duke of Burgundy.
How would Philip the Bold deal with the immediate consequences of losing his primary heir?
How would the minority of Philip III play out? How would Burgundy's lack of a proper leader influence French politics in the period that would historically lead to the murder of Louis of Orléans?
Would the Burgundians still be able to carry out as much of their OTL scheming and opportunism in the Low Countries under these circumstances?