Islam has always had bloody borders. Jolo was always on the Muslim side of that border, which pretty much runs through Zamboanga, about 100 miles north.
This is just one more episode in whats now a 450-year old war.
It’s a 1397 year war launched by Mad Mo in 622 A.D.
Took them a while to conquer all the way to the Philippines.
They almost took France in 732.