The judged pointed out that:
Texas didn't bother to educate parents about content filtering tools, or at the very least, they didn't put this as an argument in the lawsuit.
This meant that it wasn't the least intrusive possible measure they could have taken.
Verifying people's government identification also means the government might monitor what content someone is viewing, and that this has a substantial chilling effect on free expression.
Also, the First Amendment applies. #FreeSpeech