And the Spain of today is hardly the Spanish Empire of the 18th Century. The San Jose was once their possession but they lost it to history just like they lost Cuba, Louisiana, the Philippines, all their Caribbean islands, Mexico, all of South and Central America, and all their other imperial holdings. The treasure on board that ship is from Imperial Spain's colony in Colombia and since Colombia is now independent from Spain it is rightfully Colombia's decision what to do in terms of making deals with the salvage company. Spain is acting like that forgotten great uncle that no one knows who only shows up if he hears someone in the family has won the lottery or is giving stuff away.