Why Cervera obeyed a fatal breakout order

Why did Cervera obey an order he knew would destroy his squadron?

Because the governor-general was the legitimate civilian authority; after exhausting his objections, Cervera could either rebel or carry out the order, and he chose to obey.

Cervera had argued repeatedly that taking the squadron out of Santiago would destroy it. Once Governor-General Ramón Blanco issued the order, however, Cervera faced a choice between rebellion and obedience to a legitimate civilian authority. He obeyed while making clear that he understood the likely cost to ships and crews. His prior objections did not change his decision to obey once the order stood.