Normandy added a new front in the war and the threat of another invasion attempt across the channel. In 1590, the Spanish landed a considerable force in Brittany to assist the French Catholic League, expelling the English and Huguenot forces from much of the area. Henry IV's conversion to Catholicism in 1593 won him widespread French support for his claim to the throne, particularly in Paris , a city that he had unsuccessfully besieged in 1590. However, in 1594 Anglo-French forces were able to end Spanish hopes of using the large port of Brest as a launching point for an invasion of England by capturing Fort Crozon. The French civil war turned increasingly against the hardliners of the French Catholic League. With the signing of the Triple Alliance in 1596 between France, England and the Dutch, Elizabeth sent a further 2,000 troops to France after the Spanish took Calais. In September 1597 Anglo-French forces under Henry retook Amiens, just six months after the Spanish took the city, bringing to a halt a string of Spanish victories. The first tentative talks on peace had already begun before the battle. The League hardliners started to lose  ground and popular support throughout France to a resurgent Henry. In addition Spanish finances were at breaking point because of fighting wars in France, the Netherlands and against England. Therefore, a deeply ill Philip decided to end his support for the League and to finally recognize the legitimacy of Henry's accession to the French throne. Without Spanish support the last League hardliners were quickly defeated. In May 1598, the two kings signed the Peace of Vervins ending the last of the religious civil wars and the Spanish intervention with it.
Question: Why did the Spanish intervene in these religious wars?
Answer: assist the French Catholic League