If history is to be believed the combo of Vincenzo I Gonzaga, duke of Mantova's spending, the plague, and the War of the Mantovan Succession was the death knell for the state of Mantova. An interesting side effect was Giulio Mazzarino ending up in France. Now there are numerous ways the war might not've happened:
1. Francesco IV survives his attack of smallpox in 1612 and fathers a surviving son.
2. Francesco's infant son Ludovico survives whatever killed him.
3. Ferdinando acknowledges his son by Camilla Faà as his heir and said boy survives
4. Ferdinando has (a) child/ren by Caterina de Medici
5. Vincenzo II marries again after the annulment of his first marriage.
What do you guys think?