I don’t think there is a correlation between struggling doctors and grades. If anything, it will probably be the other way around.
And as your example shows, the doctor was around 50. You’ll never see a doctor in his 30s who will be happy about his financial situation
In any case, a doctor starts to make good money only after his 35th brithday. And really good money after his 40th. By comparison, someone who majored in a business/commercial field has much brighter chances of making good money around his 27th and really good money around his 32nd