Basically to protect the rights of the people
Competing conquistadors arrived and fighting broke out which killed half the Spanish in 1519. Then later in 1521 European diseases killed most of the Natives which allowed Cortes to lead a brutal attack and succeed.
Adopted a lottery system for selection
The encomienda system was a way for the Spanish Crown to maintain order and control over its colonies in the New World by using slaves in coal mines.
The most suitable option is they believed that the Church had moved away from its core teachings and became corrupt.
Between 1400 and 1500 occured significants changes in the Roman Catholic Church. During this period, people criticized that Cardinals and Popes were concentrated in worldly issues instead of caring for faith. They lived more than kings living in luxury while peope starved to death and many of their practices did not match with what the Bible said. These are the reasons why people wanted to reform the Catholic Church.