Why Manila Bay's shore batteries barely fought

Why did so many Spanish shore batteries fail to fire at Dewey's squadron?

Many were unprepared, unmanned, or judged unlikely to hit while exposing themselves to accurate return fire, so their nominal guns never became effective defenses.

Some shore-battery officers doubted that their unprepared guns would hit Dewey's moving ships but expected return fire to find them. Damp powder and absent personnel further reduced their ability to fight. Several positions therefore had guns without the preparation needed to use them effectively. The same readiness failures that weakened the Spanish squadron also undermined its shore defenses.