Henry's first wife was Catherine of Aragon and she was his brother's widow. Henry and Catherine only surviving child was a girl (Mary I), Henry wanted a son to succeed him on the thrown and Catherine was unable to give him anymore children. Henry also wanted to marry his lover, Anne Boleyn but her nephew, Holy Roman Emperor Charles V was strongly opposed and he was holding Pope Clement VIII prisoner so he could not approve the divorce without displeasing his captor.
Another obvious reason was to do with religion. Henry may have been sympathetic to ideas of protestant, Martin Luther and therefore rejected Catholicism. It was also known that monks and priests lead immoral lives. When joining the clergy they had to promise to live as poor people, they were to have no worldly possessions and had to swear to complete chastity. Maybe he did not agree with the payments people were forced to make to the church.
These payments made the Catholic Church extremely unpopular with many people as they thought it was morally wrong. The people of England wanted to abandon the Catholic Church in favour of Protestantism and Henry was very keen to be popular with the people of England.
Henry had recently spent a lot of money on wars and become bankrupt. He realised that this left him in a weak position. He also realised that churches and monasteries were receiving a lot of money. People left money to monasteries when they died, paid for specials Churches in there names when they died where songs were sung for soul, which...