I think it goes deeper than that. It is part of their chosen identity. There is a difference between doing a job and being the job. If you are doing a job, you can complete it. If you tie your identity to “protecting people from <insert thing here> you have to keep a belief going that whatever that thing is, it can never be accomplished. Even worse, when it truly had been your psyche will know and you will feel “less”. So you invent new things or redefine the thing to preserve the identity you chose.
For a different example of this consider the fireman who becomes the arsonist so he can put out the fire. This isn’t uncommon and is decently understood. We also see it these days in people who feel they need to be oppressed or “under assault” so they fake being assaulted or threatened. I refer to this as “identity bias”
At the core of this in these people is a failed locus of control. They lack control over their own emotions, desires, and behavior so they seek to control others. I call this “emotional rent seeking”, which might only make sense with some economics knowledge but I think it fitting.