Early guys like John Wyclif, Jan Huss, Erasmus, and Thomas More paved the way for thinking of how things could be done differently in the Church or at least of Christianity being different than how the Church taught (heretical views according to the Church).
Luther was an Augustinian monk and a pretty devout one at that.
He was on his way to becoming a prominent lawyer (which very much pleased his miner father) until he got caught in a violent thunderstorm and swore he would enter the monastery if he survived.
He lived and followed through on his oath (which very much dis pleased his miner father).
As a monk, he gave his life over to severe dedication and privation, hoping his devotion would reconcile him to God. It only served to emphasize his sinfulness and separation from God, however, and starting around 1510, he came to the theology that salvation is a gift of God that comes through faith alone.
Luther was especially put out by the sale of indulgences.
According to Catholic theology at the time, if one sinned, you could repent and be given the sacrament of penance. While the blame for the sin is gone, the sin is not erased and you must still be punished for it through temporal punishment on earth or in purgatory. God’s justice demands it.
You can, however, lessen the amount of punishment by performing acts of merits (you gain heaven through Jesus, not the act – you merely lessen the punishment through the act).
You can also be spiritually assigned merit by the Church via its treasury of merit. This is typically done through prayers and such. This transfer of merit is an indulgence .
Johann Tetzel, a Dominican friar, was given authority by Pope Leo X (yes, the Medici one) to sell indulgences in order to build St. Peter’s Basilica in the Vatican (you know, the one with the big dome).
Luther was put out AND cheesed off.
Tetzel A 1517 indulgence from Tetzel that reads, “By the authority of all the saints, and in mercy towards you, I absolve you from all sins and misdeeds and remit all punishments for ten days.
Luther’s actions didn’t go over well with the Church, but it was relatively slow to act since it didn’t take him all that seriously. As far as they were concerned, he was just a rebellious monk who needed to be whipped back into line.
Pope Leo X sent some theologians north hoping to quell the disturbance. He referred to Luther as a drunken German who will change his mind when sober.
Once word gets out, though, it’s too late to stop it. Luther only becomes more radical, rebellious, and insistent.
Luther’s is tried for heresy and the Edict of Worms is issued, but he gets out of town and comes under the protection of Frederick the Wise, the ruler of Saxony.
The peasants were trying to apply Luther’s ideas of egalitarianism to the social sphere. Luther came out against them and the German princes crushed the revolt, killing around 100,000( !!! ) peasants in the process.
The political aspect of all this is that some of the German princes used the Reformation as an excuse to throw off the yoke of the Church and gain power over their realms. This led to a series of wars until the Peace of Augsburg in 1555.
The Peace declared that princes could decide what religion would be practiced in their realm: Lutheranism or Catholicism (and only those two).
Henry needed a male heir. Unfortunately for him, his wife, Catherine of Aragon (daughter of Ferdinand and Isabella of Spain) bore him only one daughter. She had other children, but they were either stillborn or didn’t live long.
When Catherine turned 42, he was fairly certain no male heirs would be forthcoming. Thus, he needed a new wife.
The Catholic Church didn’t permit divorce, but it would grant annulments, which essentially say the marriage wasn’t legal to begin with.
Henry tries to get his marriage annulled on interesting grounds in 1527. It doesn’t work because Pope Clement VII doesn’t want to cheese off Spain and especially didn’t want to cheese of the HRE Charles V (Catherine’s nephew) whose troops were kinda occupying Rome at the time.
So, Henry still needs a male heir, but can’t get a legitimate one without a new wife, which means divorcing his current wife, which the Catholic Church won’t allow, or annulling his marriage, which the pope won’t grant.