I think you're misreading him. He isn't saying women can't be successful, he's saying diversity isn't REQUIRED for success. And his correctness is self-evident. He stated facts. Could there be a statistical difference if women had been afforded the same options as men in this time? Yes, it's very possible. However, that doesn't negate the fact that low-diversity organizations have been successful in the past, proving that diversity isn't a requirement for success.
Please don't read this as 'low-diversity is good'. I don't believe that, I believe that if 90% of the best candidates for a job at Nasa are gay black women then I believe that 90% of Nasa should probably be gay black women. Go with merit, ignore skin color, sexual organs, and which of the aforementioned sex organs you enjoy in others.
People are people and forcing diversity for diversity's sake does no good when the majority of all candidates for a job will have a similar collegiate and intellectual background. That ISN'T diversity, it's expanding your color pallet. We should be hiring for qualifications.