There are always numerous exceptions (that prove the rule), but the reality is that people that achieve greatness in solitude can only do so because they are in a context that permits it, i.e., civilized society which requires strong families to exist. For the vast majority of people seeking greatness they are doing so so that they can benefit society to enrich themselves and their progeny and many, many of those people are doing so to attract and keep partners to have children. It’s a basic biological fact that most motivations toward valuable output are in service to the next generation.