Why are there so many gay men in the fashion industry?

First, the fashion industry has traditionally been more accepting of openly gay men as opposed to other trades.  Even today, it is more challenging for an openly gay man to reach the level of CEO or principal than their straight male collegues.  On the contrary, a gay man in fashion can be a respected and revered leader of his field and achieve a great deal of personal and monetary reward without encountering the prejudices that are often found in other vocations -- such as police, firefighter, military or sports. 

Some good examples of this would be Valentino Garavani, Yves Saint Laurent, Perry Ellis, Marc Jacobs, Karl Lagerfeld, Alexander McQueen and Gianni Versace -- to just name a few.  Times are changing and greater acceptance of "The Gays" has led the way for gay men to excel in traditionally straight male fields, but real-world examples remain few and far between - often only in cities or countries where gays and lesbians enjoy greater equality with their straight coworkers. 

The glass ceiling that exists for women also exists for gay men, who are typically underpaid for the same work their straight male coworkers perform.  It should also be said that because they were men, gay men in fashion and design were once privileged over women who attempted to break into the field.  Although she was an exceptional exception, Coco Chanel was one of the few women who was able to succeed in an industry once dominated by gay men like Christian Dior and Cristobal Balenciaga.  So both homophobia (against gay men) and sexism (against women) in the culture at large were likely factors in gay men achieving and maintaining dominance in the early stages of the modern fashion industry.

Second, gay culture rewards creativity.  The heroes in the gay community are generally not the rugby players or the firefighters - although they do exist - but the drag queens, the musicians, the filmmakers, the writers, the actors, the artists, dancers, etc.  This is partly due to the fact that these were once the only careers gay men could excel in while still maintaining a sense of who they are and an exuberant pride in what they could accomplish. 

 This lean towards the creative arts is enhanced by a sense of uniqueness many gay men grow up with in a predominantly heterosexual world.  Perhaps this sense of uniqueness is no longer as pronounced as it once was, but I believe this outsider's perspective continues to be conducive to thinking "outside of the box" -- a trait one would prefer in a creative setting, such as fashion design.  Some would call this "bringing one's gay sensibility."

An important point: Gay men's admiration of beautiful, elegant and powerful women cannot be overstated.  Despite a sometimes undercurrent of misogyny within the gay male community, the elevation of beautiful women to mythic proportions is ingrained within the DNA of gay culture.  It has been said that a man who designs beautiful clothes for women either "wants to be with the woman or wants to be the woman".  From my basic understanding of the lives of various gay male designers, I find the evidence lacking in support of this statement. 

 There's nothing in the personal lives of Yves Saint Laurent or Valentino which suggests they are simply repressed transgender individuals.  On the contrary, Valentino has for decades designed spectacular clothes for women not because he wants to be one, but because he says "I know what women want.  They want to be beautiful."  It is this passion and eye for beauty, as well as sheer creativity and talent, that is at the core of what makes a successful designer, be they straight (like Oscar de la Renta or Ralph Lauren) or gay (like Alexander Wang or Giorgio Armani).