Why modern warships can outweigh older armoured ships

Why can a modern Type 26 weigh as much as a World War II light cruiser despite carrying little armour?

Modern displacement is driven heavily by sensors, computers, electrical generation, cooling, wiring, and missile-system volume rather than armour alone.

A Type 26-sized combatant devotes substantial weight and volume to computers, sensors, and their supporting systems. Electrical generation and distribution must supply the weapons and electronics, while cooling requires additional equipment. Copper cabling and copper heat exchangers contribute to the weight. Mark 41 vertical-launch cells also require considerable space, so removing the armour carried by an older cruiser does not produce an equally large reduction in modern displacement.