The main reason for this is Spain's own decline, leading the Spanish Government to repeatedly reduce its emphasis on the Navy, to the point where they barely develop the Navy anymore.
After the four major shipyards lost domestic orders from Spain, in order to survive, they could only find ways through foreign warship orders, or by building civilian vessels that were needed by the public.
However, the tonnage of civilian ships was very small, with the smallest being only a few tons. While military ships had evolved into ironclads, most civilian ships were still wooden ships wrapped in iron, some not even having iron plating.
Building such civilian ships didn't earn much money, and with income decreasing, the shipyards could only reluctantly scale down, even waiting for the day of bankruptcy.
As Spain's largest shipyard once, the Royal Guanizuo Shipyard had very rich shipbuilding experience and once possessed the most advanced shipbuilding technology.
