Why the Royal Navy studied an all-big-gun armoured cruiser

What prompted the Royal Navy to study the all-big-gun armoured cruiser that became Invincible?

It sought a faster all-big-gun commerce-protection ship able to kill every existing armoured cruiser, backed by confidence in British construction capacity.

The Royal Navy continuously supported competing design studies rather than moving through one unanimous institutional plan. One faction sought to do to the armoured cruiser what Dreadnought did to the battleship: concentrate heavy guns and add enough speed to dominate existing opponents. The mission was imperial commerce protection, giving Britain a ship that could catch and destroy any rival armoured cruiser sent against trade. Coal endurance and Britain's global coaling network strengthened that concept. The risk was setting a new international standard, but British leaders trusted the nation's shipbuilding capacity to match or overwhelm any response except perhaps a fully mobilized United States.