If you monitor fashion industry, you'll likely find a huge majority of woman-employees. Are these companies  supposed to address the causes (I don't know, women more interested in fashion?... more esthetically fit for fashion shows?... no idea).

Well, you can find men in the fashion industry, there are male models, male designers seem even to dominate. Where the men are missing are in the low salary jobs like seamstresses. Unfortunately, it seems still to hold true that female dominated jobs usualy are lesser paying jobs, like chasiers in supermarkets - you find rarely any men. And and even when there are both genders doing the same kind of job there still is no pay equality, men still earn more for the same job. So yes, I think it is up to businesses to offer same salaries for the same jobs, that would create more equality and I assume also what you would call better diversity.