It's really more a matter of degree than of a sudden swing in ideology, really. So long as libraries were generally aligned with the most conservative elements in their area, those elements left the library alone and didn't attack them as subversive or liberal, because it was still generally in the frame. Now that at least some libraries are visibly breaking with those antidemocratic, white-supremacist ideals, the attempts at punishment to bring them back in line, like this, have been swift and high-pressure.