The Protestant Reformation happened because Church leaders were too wealthy, some unholy, and people had problems with the faith.
You have everything and we have nothing!
During the middle ages, the Catholic Church was very powerful, but some people had criticisms for the church. Martin Luthor wrote them down, Sola Scriptur.
The differences between Protestants and Catholics are, Protestants don't believe in a pope figure, Catholics do. Protestants don't have the Eucharist, Catholics do.
In response to the Protestant Reformation, the church instituted the Council of Trent. This was to define the teaching of the church, address abuse and corruption, and to regulate the priest' training.
We want changes!
How about the Counsil of Trent?
Martin Luthor believed in Sola Scriptura, Sola Fide, Sola Gratia, and Sola Gratia.
The church says that the problem with Sola Scriptura and Sola Fide is that it goes against tradition and scripture.