Why did Francis I become heir to the French throne in 1498?

Francis I became the heir presumptive to the French throne in 1498 upon the accession of his cousin, Louis XII.1

This succession was governed by the Salic Law of Succession, a fundamental principle in France that excluded women from inheriting the throne and prohibited descent through the female line from constituting a valid claim to the crown. As a member of the Valois-Angoulême branch of the royal house, Francis was a direct male descendant of the Valois dynasty, which had ruled France since 1328. When Louis XII—who belonged to the Valois-Orléans branch—took the throne in 1498 without a male heir, Francis, as the next eligible male in the royal line, became the heir presumptive.231