A reply to /u/mb496

There are three reasons, although the failure of Spain to maintain a large foothold in North Africa is not from lack of trying. Similarly there was no lack of ideas to bring the fight to North Africa and even to the Holy Land. The exploration of the Americas was originally sold as a way to flank around to the Holy Land.

First is that successful invasion of ports and outposts across the strait was very difficult. Even more difficult is the challenge of securing them over time. Moors tended to fade into the southern inhospitable lands to bide their time to strike again. This pattern continued to the late 1600. Spain and Portugal could only keep very few outposts such as Ceuta.

Second is regime change. The Trastamara dynasty of Isabella d Ferdinand was succeeded by Charles V of the Habsburg dynasty, who also had inheritance elsewhere in Europe. Therefore the focus shifted.

Third is a new set of opportunities and challenges elsewhere. The discovery of the Americas and war against the Dutch and English meant Spain had to maintain two navies, one in the Mediterranean and one for the Atlantic Ocean and beyond.

More of this can be found on my profile page.