As for Ngannou, I think Dana White could be starting to regret his decision on not allowing Ngannou fight in boxing. In one interview he said that Hunter Campbell regretted the decision because Hunter really wanted to keep Ngannou in the UFC. Dana White said he had no regrets. But as a businessman he prolly did. Ngannou's match vs Fury would've brought the UFC's stock up imho.
You could argue that the Fury fight brought UFC's stock anyway. In the eyes of the public opinion, Ngannou is still associated with the UFC despite not having a contract.
And I'm having a hard time imagining how such allowance (to let him compete in boxing) would even work. Would UFC want a share of the profits? I know they've done it with McGregor, but no idea how was that sorted from the contractual side. McGregor was on clear decline after the Mayweather fight, so no wonder UFC didn't love the idea.
Anyhow, things turned out surprisingly nicely for Francis. He probably will earn multiple times more than what he'd get by staying in the UFC for the rest of his career. Well done to his manager.