The Pope ceased being powerful when Catholics ceased believing in Papal power.
The same thing happened to the communists in Eastern Europe. One day everyone realized they were not the omnipotent masters they had presumed to be and their power evaporated almost overnight.
With the Pope there was no physical empire to lose so the losses were less rapid and less dramatic, but losses all the same.
> With the Pope there was no physical empire to lose so the losses were less rapid and less dramatic, but losses all the same.
The Vatican has owned and/or controlled a huge financial empire.
There was an empire to lose, though. The Papal States covered a good chunk of Italy until the mid-19th Century,losing them when the Popes aligned themselves with with the House of Savoy and the Kingdom of Sardinia and against Garibaldi’s republican forces.