" So that’s what it takes to get Snape on probation. Not bullying Neville, not favoritism, but refusing to fight Harry Potter. Umbridge expected him to comply; unsurprisingly, Lucius Malfoy seems to have been bribing Umbridge, encouraging her to purge Harry’s allies from the staff, expecting fellow Death Eater Snape to cooperate from the inside. "

― Lorrie Kim , Snape: A Definitive Reading