Not OP but deeply nonreligous and the idea of a CEO dating subordinates sounds very unprofessional and cheating on a partner sounds generally shitty. (Maybe that's not exactly how it went down, but if we take the "left their wife" line literally.)
Basically, it isn't the divorce that's the problem, it's everything else about it.
CEOs dating subordinates is hardly uncommon. Melinda French met Bill Gates while she was a product manager at Microsoft. That seems to have gone well for both parties. I've worked with a few executives who were employing a significant other in some form or another. Admittedly this sort of thing can go very wrong, but I think there are much bigger sins a CEO can commit...
The difference there is that Bill Gates was not already married. The difference there is that the role of product manager is much more skilled than the position of secretary. A product manager has the freedom to take the lead on big projects. A secretary is such a submissive and typically gendered role that companies have started to shy away from using the term at all. Now they are opting for "assistant" instead, implying a more equal footing between the employer and the employee.
FWIW, I'm not sure why infidelity is so stigmatized. With all the things going on in the world that seems so minor in the grand scheme of things. Also, presumably the secretary is an adult, so they're two consenting adults (yes, I understand the power differential issue but there's also the risk of being accused of sexual harassment, which I'd argue is more damaging nowadays). Relationships are so complicated I've learned not to pass judgment on anything.
I'm definitely not saying infidelity is good, only that I think it's treated way out of proportion.
To be honest, I think it sounds more shitty to unilaterally declare respect or lack thereof for a colleague based on their private life rather than their professional performance.
Take credit for work that's not yours, and leave with millions in severance after they've fucked up the company? Totally fine. Sleep with your secretary? Unforgivable (and the CEO's fault).
My comments about infidelity should be read from the POV of a young programmer, that knew nothing about entrepreneurship, starting or running companies, who looked up to C-level management, who's entire network was filled with people in blue collar, low paying jobs.
And who was stunned to realize: (1) they are ordinary people, (2) aren't supermen in any way, (3) that many of them valued themselves, money and power more than anything in life, and/or seemed to have no ethics whatsoever.
Basically, it isn't the divorce that's the problem, it's everything else about it.