Why would pro-LGBTQ+ companies like Snap and #Microsoft endorse #KOSA? Business is business! What's important is looking like they're trying to protect children -- even though KOSA would actually harm kids.
Politically, KOSA's anti-LGBTQ+ aspects gives Republicans (and anti-LGBTQ+ tech companies) a reason to get on board. If some of the Democrats who say they're pro-LGBTQ+ Democrats "reluctantly" decide to support it then it's got the votes to pass. On the other hand, if pro-LGBTQ+ Democrats and legislators of both parties who really do want to help kids stick to their guns, then Congress is a lot more likely to do something that actually helps kids.