It was enabled by the invention of the printing press the century before, and was a period of both internal and external questioning in the Church which addressed some (but by no means all) of the issues of corruption in the Church, and resulted in the setting up of the protestant Christian religions.
From a marketing point of view it largely removed the Catholic monopoly on Christianity. Christians who did not wish to renounce their Christianity could take the much less drastic step of converting to another form of Christianity. Thereafter, the Catholic church had to lift its game or lose market share. It did a combination of both.
See