Both genders contributed to killing it. But, basically, since men will do most anything to impress women the leading reason why it ended is the men noticed the women either:

a) labelled them as sexists for doing it, or

b) took it for granted or ignored it, or

c) did not reward it (meaning the chivalrous men did not get the girl, and maybe later saw them choose the unchilvarous man over them).

Personally, I still do most of it but I do it universally for all (meaning I'll hold the door open for anyone, not just a woman). Because then if they do "a" and say I'm sexist I can honestly say no, I do it for everyone, and if they do "b" and don't care it doesn't bother me because I know I just did it to do a universally good thing. "c" doesn't really apply to me since I'm already maried.

I don't think it's dead and I don't think women in general diminished it. I think the ultra-elitist Feminazi's are doing their best to destroy manners and chivalry as their means of gender equality and I think they are dumb as a bag of rocks for doing it. If a man holds open the door for me I am going to thank him.

Chivalry back in the day was to be nice to women, which has become almost non existent as it has been misinterpreted as men thinking women need "special help" in day to day activities. I think the sides on this debate should have been "feminists" and "non feminists".