The idiom "Behind every great man is a great woman" is defined as an expression in use at least since the mid-1940s.
The woman in question usually is a wife or a mother; the observation is that no man gets to be "great" in a vacuum, and some woman, somewhere, had a hand in the man’s success.
(idiom)An example of "Behind every great man is a great woman" is how Elinor Roosevelt supported the ailing Franklin Roosevelt by doing a lot of his public appearances and developing many of the popular positions held during Roosevelt's presidency.