I think marital infidelity is shitty behaviour but I also think the main issue here is that this man in this job with this global significance thought this woman was safe to be involved with.

His board must think he's a lunatic. They have every right to know if he's having an affair with anyone (because marital infidelity is a personal corruption issue that is rarely not a problem when it's a CEO, since carrying off an affair usually involves suborning staff in some way). But this? Madness.