What change inspired Girolamo Savonarola to begin preaching prophetic sermons?

Girolamo Savonarola’s shift toward prophetic preaching was sparked by a sudden revelation. While he had previously served as a lecturer at the convent of San Marco in Florence, he was initially unsuccessful as a preacher.1

Following this inspiration, he began delivering sermons during Lent in 1485 and 1486 at San Gimignano, where he introduced his famous prophetic propositions: that the church was in need of reform, and that it would be "scourged and then renewed". These themes of divine punishment and moral purification remained central to his ministry throughout his career.12