I think you are ignoring substance abuse and domestic violence in those numbers both of which are higher for males and are no respecters of income.
Men do not want to hear this, but they have a higher rate of risk taking behavior, higher rates of violence, murder rates (as both perpetrators and victims) mental illness, and most other negative social or health risks. All of which impact their ability to sustain a marriage.
But the real dirty secret is that overall 50% divorce rates are driven by a hard core group of serial marriers/divorcers who are chronic failures at marriage, yet continue to remarry. This group is mostly made up of not losers, but grifters, narcissists and sociopaths of both genders who never seem to marry each other but burn a wide swath through the rest of the population all while squealing and blame shifting.
Yes, but the risk of those things is LOWER among college grads than non college grads, so again that doesn’t explain the shift from roughly 50/50 to 90-10. It has to be something fairly unique to college educated couples.
And yes, the overall divorce rate for first marriages is a bit over 30%, not the overall 50%. But, the marriage rate has also declined considerably in the last 50 years, so only the “stronger” relationship marriages are likely occurring or the rate would be even worse and more couples just live together without getting married.