Why early steam cruisers still carried sails

Why did early steam cruisers carry such extensive sailing rigs, and why did the rigs disappear?

Sails protected global cruisers against unreliable coal supply, but improving coaling networks let designers clear the centerline for turrets and modern armament.

A cruiser could not risk becoming immobile at a distant station simply because no coal was available, so even 1880s ships retained substantial masts and rigging. That insurance occupied the centerline and interfered with turret arcs. As coal became easier to procure around the world, navies could remove the rig and use the newly available deck space for centerline guns. The exchange makes propulsion infrastructure a direct cause of changes in cruiser silhouette and armament.