Why Crows Nest cannot replace a ship's targeting radar

Why build dedicated radar ships when Crows Nest and future airborne sensors already provide warning?

Airborne sensors can search and cue the force, but dense missile defense still needs rapid targeting data from a powerful radar close to the command and weapon systems.

Crows Nest provides airborne early warning and can direct attention toward a developing threat. A future fixed-wing uncrewed aircraft may carry the next version of that search radar. Search tracks are different from the detailed targeting data needed to allocate weapons against several fast threats arriving together. Turning on the ship's large radar reveals its position, but it also keeps processing and fire-control data close to the command system. Hypersonic weapons, cruise missiles, and drones timed to arrive together create the largest data load at the moment when delay is least tolerable. That is the strongest reason to retain a major radar on the defended ship even when airborne warning exists.