The heydey of conservative news is when there is a Democrat in charge. I've seen several conservative talk radio stations move over to sports. Others have moderated because conservatives aren't as angry/frustrated/outraged as before Trump took office. So they are shifting to personalities like Dennis Prager, Michael Medved, people who are holding deeper conversations on values and culture versus "OMG, did you see what the Democrat did today?"
Getting rid of OReilly to put in a younger and less provocative personality would fit that trend, while using sexual harassment as an excuse lets them put in a cheaper person like Tucker Carlson while gaining social points.