Why did Henry of Navarre become heir to the French throne in 1584?

Henry of Navarre (the future Henry IV) became the heir presumptive to the French throne in 1584 due to the death of François, duc d’Anjou, the youngest brother of the childless King Henry III.12

Because Henry III had no children, the death of the duc d’Anjou left the Protestant Henry of Navarre—a distant cousin and member of the House of Bourbon—as the next in line for the throne according to the Salic Law of Succession, which excluded women and those claiming through them from the French monarchy. This transition triggered the War of the Three Henrys, as the Catholic League sought to prevent a Protestant from succeeding to the throne.34215