I don't know why he did that. People do stupid things all the time.
Centuries of gender discrimination, in a field that is very publicly plagued by it, in a world that is still broken with it, what was Damore thinking?
Everyone has the freedom to act, but no one has freedom from the consequences of the act.
No question that Damore made mistakes; most sane people would never have let an opinion like that touch paper during office hours, and google will hopefully review the terrible idea of having a 'controversial opinions' forum.
However, his mistake is the debate's gain - the response is clearly disproportionate on several levels. This is an opportunity to identify the people calling for his life to be destroyed and convince them that their definition of various -isms is calibrated a little too high. Or failing that, to try and get some moderates into positions of power rather than the hard left.
Did he leak the memo to the press to cause the outrage? No he didn't, so he is not responsible for the PR whirlwind created by it. Those who leaked the internal corporate communication are responsible and they should be fired.
Unless i missed something, the guy never advocated violence or gender discrimination, or making anyone's life miserable. He expressed opinion on scientific explanation. You may find it very stupid, but what in your mind makes you think it's OK to destroy a man's life for his opinion, and then i suppose pretend to be someone with high moral grounds.