During this time period the catholic church was selling indulgences as easy repentance to get into heaven. You just had to give a little money to the church and you, or a friend, or a dead relative could go to heaven without having to go to confession. Martin Luther saw this and was appalled because it went against the teachings of the bible. He then posted the 95 theses, which were complaints on the current conduct of the church, on the cathedral door. This led to others questioning the church.
Martin Luther later translated the bible from Latin, which was only read by clergy and scholars, to German the common language of the people in that area. This along with the printing press gave common people a chance to learn for themselves what the bible was saying. Regular men could achieve salvation by themselves without paying for their repentance. People began to be most individuals rather than just blind followers of the clergy.
I think that artists also began to be more individualistic and we see fewer religious works of art. There are more still life paintings, portraits, more of a focus on man rather than God as the pinnacle of all things. So we see this change from the church as well as from the traditions of painting. With this art becomes less controlled by the way things should be portrayed and more open to exploration. New techniques are developed because you can make whatever you want, and creativity flourishes.