The most important thing to remember here is how much economic power the Church had. The Church had huge land holdings (many of them held by monastaries) and also brought in large sums of money from donations and fees for various religious services. Popular unhappiness with the greed of many church officials, along with the desire of rulers to get their hands on money that was going to the Church, helped to cause the Reformation.
Many church offices were sold to the highest bidder or given to favored people. These people would take in all the profits from their offices and use some of the income to hire poorly trained and paid clergy to take their places. These clergy would often do a bad job, leading to unhappiness with the absentee officials.
At the same time, the Church was drawing off much of the money that the people had. This was money that would not go to the secular rulers of society. The governments did not like seeing money that could have gone to them going instead to the Church. This, too, made some of them likely to support the Reformation.
In these ways, the Church's economic wealth and power helped lead both the people and many political leaders to wish to oppose the Church.