Protestants differed from Catholics by insisting what about the priesthood?

Protestants differed from Catholics by insisting on the "priesthood of all believers," which emphasized that all Christians have direct access to God without the need for a mediating priest. This belief challenged the Catholic Church's hierarchical structure and the unique authority of ordained priests. Protestants argued that individuals could interpret the Scriptures and have a personal relationship with God, thereby diminishing the priest's role as an exclusive spiritual intermediary.