Mary I was Queen of England and Ireland from July 6 or 19, 1553 until her death on November 17, 1558. She is known for her attempt to repeal the Anglican Reformation, which had begun during the reign of her father, Henry VIII. During his reign he fought to restore Catholicism, executing hundreds of Protestants in England and Ireland, earning the nickname of Bloddy Mary
That is because Engels presented things much worse than they actually were so as to prove a point and spread his ideology. Of course that a little bias was necessary for that since it had to motivate people that they had it worse than they really had it.