Why did Basque remain more stable in the French Basque Country after the 16th century?

In the French Basque Country, the Basque language has remained remarkably stable since the 16th century, with its geographic extent today being practically the same as it was then.1

While the language faced significant pressure from Castilian Spanish in the south beginning in the 10th century, the northern region experienced different linguistic dynamics. In the north, French emerged as a more modern rival compared to the long-standing pressure from Romance languages in the kingdom of Navarre. The stability of the language in the French Basque Country is largely attributed to the region's historical character; it remained a more rural, less urbanized area compared to the industrial centers where the language has struggled for survival since the 1800s. Additionally, the Basques historically retained a large measure of local autonomy and privileges, known as fueros, which helped preserve their distinct cultural and linguistic identity across the Franco-Spanish frontier.12