The tragic and improvvise death of Mary of Burgundy destroyed the happiness of her family (and dashed all the hopes of Emperor Frederick in having one day his own grandson as heir of Lotharingia) but unlike what many would have thought do not destroyed the bonds between Maximilian and his former father-in-law or the one with his stepson.
Sure Maximilian had returned in Austria, after his wife’s death, but without any intention to broke the bonds with her family and while he would remarry soon, like his father was loudly asking since his return in Vienna (and as that was only two months after Mary’s death, the request had done nothing for repairing the strained relationship between father and son), the Emperor would have no part in the choice (as Maximilian vetoed him to arrange his next wedding), unlike the French King Louis XI (who would deeply regret in the latest months of his life the part he played in Maximilian’s remarriage).
Louis XI of France was used to interfere in the affairs of Burgundy (and Lorraine) and was rather unwilling to accept the fact who he had no authority over the Kingdom of Lotharingia so after the death of Mary (and Maximilian’s departure), he returned at the attack, trying to bully his now fellow King Charles in accepting again him as overlord and pretending a wedding for his son, the Dauphin, to princess Isabelle, with a lot of lands as dowry for the bride (but he would be willing to accept also Archduchess Marguerite, naturally with the same dowry) mistakenly believing who the death of his daughter had finally broken Charles the Bold. While was true who the death of his daughter was an hard blow for Charles I, seeing his old rival menacing again his lands and their independence, had the unexpected effect of bring quickly the King of Lotharingia out of his mourning and push him to plan once for all the ruin of the Spider King.
The only problem was who he needed allies for doing that and while he was sure to being able to count on Maximilian and also of the support of the Duke of Brittany and other French nobles, he needed also to bring in his English brother-in-law, whose interest was in marrying adequately his two elder daughters (as Cecily’s Scottish betrothal was always uncertain and Louis XI’s used Elizabeth’s engagement to his son as mean for controlling Edward).
Louis XI’s intention to get one of his granddaughters as bride for the Dauphin removed half of Charles‘ problem (for getting Edward‘s agreement to another war) and he had a good idea for the other half so he wrote some letters, and pretended to be still too distraught for rebuffing Louis’ initiative and protect his lands and heirs.
As he had guessed Maximilian was enraged as him and willing enough to play his part, so the only thing still missed was Louis XI falling in his trap and making that fatal mistake who Charles was hopefully waiting.