Once again, to make it clear - the reason why people are suggesting extreme misogyny was a driving factor behind this crime is because it's the reason the killer gave.
So many times one of these mass murder events happens, and when it comes to the "why" we're basically stuck with "we'll never really know", only having to settle for ambiguous clues derived from web search histories or posters the guy had taped up in his room, or conflicting witness statements about what the guy said during the rampage or what not.
Here we have a case where the killer helpfully left this tome behind where he lays out, in excruciating, disgusting, microscopic detail, his thought processes leading up to his killing spree. Women are evil, women are animals, they don't deserve rights, they have rejected me and failed to have sex with me and for that they deserve to die, and I will kill as many of them and the men they've chosen instead of me as I can, he says. And in the face of this incredible and highly concise confession, people insist on second-guessing misogyny as his motive. Either it's "he killed a lot of people and so was obviously crazy, thus his motives aren't really that important" or "a couple of sentences in his pages-long screed against women mentioned also hating the men those women had sex with instead of him, so obviously he hated everyone the same and wasn't especially misogynist". It's amazing. Fantastical. Mind-boggling.
Seriously, if some guy were to shoot up an inner-city school and left a note saying "I shall purge this great white country of all the (expletive beginning with the letter N)s, starting with this school", would his bullets hitting a few of the white students make anyone say "well now wait a moment here, let's not jump to the conclusion that racism had anything to do with what this guy did"?