There is a strong correlation between career success and marriage. On that point, he is entirely correct.
Now, whether the correlation is due to: (1) the path to success bringing many men into contact with women they are "compatible" with; (2) that "driven" and wealthier men are naturally more likely to date and marry within their peer group or; (3) that being married actually helps men become more successful - is a bit muddy.
Many women married to successful men do a lot of the heavy lifting; whether that is editing and helping develop ideas, bookkeeping, childcare, and homecare; connections and support from marriage - or anything number of other things.
I could smoke a bag of what you are saying, but..
IMO, the latter scenario you have presented tells me that said men have a strong support system at home and so more likely than not, their marriage is healthy. However, you also have a lot of people who are in unhealthy marriages.
I don't believe that a married man is more likely to be successful just off the strength of being married. A lot of people move up the corporate ladder of success based of who they know, who they blow or was simply at the right place at the right time.
What I can agree is that a man who is in a happy supportive marriage becomes more focused and driven to succeed because he have people he loves dearly that depends on him. That drive to provide is what creates a strong worth ethic which is a great thing..
But, a man who is single(by choice) can also be successful whether it is in a corporate setting or blue collar/labor setting.
If I was in a position to hire a qualified candidate for a high position, I am not gonna base my decision solely on his marital status. My focus would be based on his credentials related to the job and other factors unrelated to whether he is married or not.
Happy people have a better chance of becoming successful than people who are not happy whether they are married or not...