Many times it was to get property. If a landowner died and had no children his wife would inherit the land. If that woman were to die before remarrying and having children, then the lord of that area would get that land. If that woman were to be accused of being a witch, then that same Lord would preside over the trial and determine whether the woman was guilty of witchcraft. I think you can see a conflict of interest here.

Check the history of Luxembourg. It got so bad the Church had to step in. Now the church wasn't a great defender of women's rights, but this kind of thing got so bad even the church had to say "ok you're taking this too far."

But sometimes it was for petty reasons. Someone in town hates a woman for whatever then accusations of witchcraft were made. This is kinda anecdotal, but I got an ancestor that lived in Salem, Mass. and there was a witch trial simply because a woman got re-married to my ancestor too soon after her previous husband died.

Although the poster above made a goof by mentioning Jesus, the general sentiment of the whole witchcraft thing being about killing women for horrible (and sometimes petty) reasons seems right to me.