Why did Amelia Mary Earhart go down in history?

Because of she was a pioneer - both in aviation and in social aspect (as a woman who refused to follow the social limitation for women in her era), and set some prominent and important records in the "golden" pioneering era of aviation. Also she had an attractive personality, being courageous, smart, intelligent, good-looking and certainly charismatic - that additionally attracted the people's attention to her, and made her a kind of embodiment of the best features of the American national character.