Witches are human.
Humans have all sorts of motivations.
Years ago I worked with a hideous woman. She was a manager and the most terrible bully, staff were afraid of her. She was vindictive and nasty, would waste no time in putting the boot into others. She was vicious and nasty to everyone- including me.
I came across some of her work on the system. She had made a bad mistake which violated company policy.
I could have hidden it, moved on, I could have rectified it to minimize the damage.
I did none of those things.
I engineered it so her action popped up in a report and landed in the MDs inbox.
She was disciplined and demoted, removed from her position.
No magic was involved.
I could have saved her skin, I chose not to.
People do things like this often.
I don't know why you think witches should have any more moral high ground than an average person.
They don't- they just have extra tools.