The most useful thing to know about Heinrich Kramer is that his own church stopped him. In 1485 he came to Innsbruck with a papal commission and opened proceedings against a group of local women. The bishop of Brixen, Georg Golser, looked at what Kramer was doing and intervened. The proceedings were found defective, the accused were released, and Kramer was told to leave the diocese. Golser's surviving correspondence about him is unflattering in the extreme.
That is the setting for the Malleus Maleficarum, which appeared within two years. Read against the Innsbruck failure, the book's most striking feature stops being its demonology and becomes its procedure. Its third part is an argument that ordinary criminal process is inadequate to this crime and that its safeguards must be relaxed. Kramer had just discovered, in a real courtroom, exactly which safeguards had defeated him.
He had the papal bull Summis desiderantes affectibus of 1484 in hand before Innsbruck. He had solicited it because local clergy were obstructing his commission, and it says so: the bull complains that inquisitors are being impeded. Bound into the front of the book, that complaint reads to a purchaser as papal approval of everything inside. It is a good example of why the persecution cannot be described simply as what the church believed. Kramer's authority came from Rome and his opposition came from a bishop, and both were the church.