How did this happen? I seriously doubt it's because girls in bikinis stopped being effective. But when you can't get away with sexualized advertisement without being martyred, you're going to look for similarly effective marketing that won't offend the people throwing the stones, and in my opinion they've done exactly what we should have expected in this situation.
I'm not saying it's right or that women shouldn't expect to be treated as equals. I am saying that the tech community (and several others) have tried and are trying so hard to reject sex and sexuality and any application of it that might possibly offend someone that we're finally making it worse. Before it was just an obnoxious inability to be comfortable with ourselves. Now that we've gotten to the point where everyone knows how prudish and hyperconservative we are, they've also figured out how to keep marketing to us effectively without offending our delicate sensibilities. And we're still upset.
It's a shame that so many men have such a hard time conducting themselves well in mixed professional company. It's also a shame that we are so utterly unable to be men and women without pigeonholing ourselves and harassing each other over it. It's a sad situation.