However, over time, tenure turned into a career goal-post rather than a necessary security blanket, and it's basically lost all of it's enforcement credibility, e.g., tenured professors are fired/"resign" all the time after making comments that are viewed as racist/sexist/etc.
So now that it's clear that tenure doesn't protect professor, it's not surprising that they turn to other methods, anonymity being an obvious one.
Invoking anonymity is everyone's right, but it's still sad. Professors are supposed to embody the ideal of free and open thought, and by publishing their works anonymously, it's a sorry and self-enabling acceptance of their own irrelevance.
To elaborate a bit on why I say this: Since Social Media became uniquitous as a communication medium, I have found no more helpful way to process this in just political terms than to recognize the role of social media as a virtual urban plaza. For the last 7-8 years that I have used that metaphor, it has persisted in leading me to what I believe is the most respectable and ultimately healthy assessments of the terms it should operate under.
Interestingly, the plaza had a more complicated relationship with anonymity and pseudonymity because, outside of one’s community, one could not be recognized or traced. Nonetheless, learning about the history of this is surely helpful here.