Not necessarily exclusively about money. The article below provides some insight. Public perception is also important. Believe it or not, Fox does not want to be an advocate for sexual harassment. First, Ailes; now O'Reilly. Both of them are pigs. The TL;DR version is the brothers Murdoch want to renovate the program. Rebrand, whatever. The old man was resistant to change, but ultimately rolled over.
I think it could go either way. They're running out of bankable options. Don't forget, O'Reilly has been around for 20 some-odd years (21 on Fox, to be exact). Massive shoes to fill. They don't have anybody in the stable. Remember "Fuck it! We'll do it live!"? He's a legend. [Thanks some dude on Reddit who posted the video yesterday. Nice to see it again. Amazing. Must see.]
Nearly every other blowhard on TV has flamed out or is on the verge of career implosion. Beck, Jones, and Limbaugh are finished. The racist blond lady archetype has been ruined. Milo who? The rest of 'em, the Steve Doocys of the world? Hahahaha. There is no bigger twat on the planet than Steve Doocy.
One would think, right?
When the top dog in the land is a self-admitted misogynist, it's pretty much a free-for-all down in the trenches. This has obviously been going since before you and I were born. O'Reilly was probably the biggest star in the news game. Thirteen million is nothing to him. It's a third palace in Aspen. "Fuck it! I'll write another book!"
Let us not forget that these were settlements; none of the allegations went legal. Can we trust the veracity of the allegations? Probably. It's just a hunch. If you got nothing on me and threaten sexual harassment, I'm gonna say, "See you in court." But I'm not a $200 million dollar a year cash cow. I have very little to lose by fighting. Again, $13 million is nothing. Divided by five women, gee, that's not a lot of money. If someone had really wanted to score big, they'd have filed suit already. Take your paltry $2 million and stuff it.
Here's the gist of my thoughts on O'Reilly in toto. We haven't seen the last of him, not by a long shot. Unless his private plane goes down in the Atlantic. But you know where you won't see a single mention of him? On Fox News. Check their front page. Not even a squeak.* That's fuckin' awesome and I only read Fox to get the other side of the story.
*Except if you scroll down to the very very bottom, The O'Reilly Factor is still listed as a show. The IT eggheads have been napping.