He was a disgruntled priest who was unhappy with the fact that the Catholic church was (in his view) selling dispensations, so he left to start his own church and opened up the Christian church to all of the confusion that now exists.
With his departure from the original church and its teachings allowed any nut to interpret and/or justify nearly anything and start their own church. Ask the "Snake handlers" or the Pentecostals.
I believe Luther was the one that started 'salvation by faith alone' from reading a verse in the bible. Previously the catholic church had convinced people that they had to buy little pieces of paper called indulgences to guarantee their spot in heaven. The Catholics also did not want regular people to read the bible, but to listen to it from members of the church.
He had a gripe with the Catholic Church a few priests at the time were selling indulgences he disagreed with this in this he was right, no indulgences are not practiced today. As for the rest he had help by the fact Henry VII wanted to marry his Mistress as well as divorce his Catholic wife which the Catholic Church wouldn't agree too and have a Male heir and Luther had support by German princes and their armies. Luther while he was right about the indulgences grew in power with his SUPPORT he promoted his own ideals and vision of Christianity Protestant Christianity and their are 39000 denominations of Protestant Church's today.
Martin Luther never intended to leave the Catholic Church. He challenged the selling of indulgences to pay for the extravagant lifestyle of the pope. He translated the bible into German so people could read the word of God for themselves. People began to leave the Catholic Church once they understood the church was not biblical.Martin Luther was excommunicated.
First of all let me state that the Church had a Bishop who was violating the teaching of the Church and was offering indulgences for money not for the Pope as some like to claim but for the building of a new Cathedral and personal uses.There were others in the Church who were not behaving well also.Martin Luther started out with correct intentions but eventually it quickly became a political thing and with the Princess of Germany started the Lutheran Church from which the calamity and confusion of Protestant Churches came along with Henry the V111 wanting to Divorce his Catholic Wife for his Mistress and the Church said no.To this day many Catholics leave the Church because the Church does not recognize Divorce as Christ commanded.So any way you now have a Hodge Page of competing Protestant Churches all Claiming to have had the Holy Spirit show them the way.