1. The memo being leaked.
2. After being leaked, misrepresentations and even outright falsehoods about the memo being promulgated online.
Remember, the memo was being circulated within google for a month before his firing. This suggests that Google did not see the need to take punitive action against Damore due to the memo, but rather that it was the reception of the memo by the media that made Google fire him. Anecdotally speaking, most of the people I've encountered that read the full memo (as opposed to articles about the memo) think it wasn't worthy of firing.