When you first meet someone and are deciding whether to see each other again, whether you want to or not, you consciously or unconsciously size each other up. In addition to deciding if you’re attracted to the other, you assess if you are in the same league as the other.
This league can be physical — there have been numerous studies that show people couple with others in the same relative attractiveness levels — with some obvious exceptions. Power and money (although some would say that money is power) is an exception. Thus the hot young woman with the not-so-attractive powerful/rich man. (Could be young, hot man with powerful/rich woman, but we don’t see that quite as much.)
Other elements of this league dynamic — in addition to looks and money/power — could be education, power without wealth (think politician), or fame.
When you decide to date someone you perceive as being a step or two below your league, you’ve found other characteristics that make it OK in your mind. You have lowered your standards in some area(s) because you think he has enough other attributes to mitigate where he doesn’t measure up.