He absolutely wouldn't.
He's ducking the fight. Period. If he takes it and loses, which he almost did vs Santos and vs Reyes, he couldn't say he's undefeated anymore. He'd lose a lot of his prestige and, frankly, his ego can't handle a loss. He spouts so much Christian nonsense on Twitter and then constantly cheats on his wife, does recreational drugs, cheats in all his fights...the guy is a sociopath and a narcissist. He doesn't like his chance vs Ngannou.
If he won the Ngannou fight, he could pretty much write his own checks after that. Money wouldn't be an issue. He would make Conor jealous with his paychecks.
But he really, truly doesn't believe he can do it. And he's on the wrong side of 30 after 10+ years of professional cage fighting. His prime is wasting away the longer he sits out. If he wants to get paid, he has to fight. Period.
This is not about money and never has been.