Does anyone know why Martin Luther wrote the ''95 thesis''?

Because he was dissatisfied with several practices of the Roman Catholic Church, including the sale of indulgences, the abuse of priestly power and the power of the Pope. He also argued that faith, not deeds, is the path to salvation. By making these arguments public, he sparked a religious revolution that came to be known as the Protestant Reformation.

It may have been a part of his dream that he just forgot to mention.