Suppose a female new grad goes to Electronconf and sees all male speakers. Suppose she goes to other conferences and it's the same story.
She feels there's no way she'll be able to break ground and be recognized as successful. She slowly drops out and leaves the industry and goes somewhere where she can make friends like her.
Now suppose she sees plenty of female speakers and she thinks to herself "wow this is awesome, I wanna be like her, she was like me 5 years ago". She stays in industry, and possibly becomes a speaker on future.
Once the cycle of people being motivated and seeing others like you starts, you see a diverse set of candidates joining the industry.