Why early dreadnoughts often preferred twin turrets

Why were several navies slow to adopt triple turrets?

Early designers valued the redundancy and agility of several twin turrets, but longer-range fighting later made triple turrets more advantageous.

Navies using multiple twin turrets accepted more hull length and beam in return for resilience: losing one turret removed a smaller fraction of the main battery. Twin mountings could also move more quickly than the largest early triple or quadruple mountings. As gun ranges and calibres increased, the balance changed and concentrating weapons in triple turrets became more attractive. The move from casemate secondaries to secondary turrets provides a parallel example of designers reorganising weapons once they expected to engage threats at greater distance.