Records concerning the total number of people who died at the hands of either Inquisition are very difficult to piece together. What does seem to have been the case is that far more were released than were executed. Most of the great witch hunts of European history took place after the Reformation, in Protestant countries. One historical explanation is that, once Protestantism made 'heresy' impossible, another popular scapegoat had to be found, and 'witches' were the obvious choice. Without an Inquisition which, even though rudimentary, was still a legal court, women were left at the hands of their fellow villagers, where accusation was sufficient to lead to death if she were sufficiently unpopular.
Popes are human beings, and they can sin.
What is perhaps more astonishing is that more of them weren't utterly evil. From a list of over 200 popes, there are remarkably few who have lived the high life. He was a sinner - and yet he did not try to change the deposit of God's truth at all. The truth of God protected even him from damaging the transmission of the Faith to all believers. Popes can be dreadful.