Regardless of the attached feelings, the motivation is the standard authoritarian delusion - a belief that more control will straightforwardly translate to better outcomes, or more commonly prevent bad outcomes.

We see it across our society - it's not just the politicians, but the whole mass media cum social media narratives of the government needing to "do something" in response to something bad having happened.

In reality society is not a monolithic top-down entity, but rather full of individual actors that each have their own motivations and respond to incentives in their own way. The idea that lawmakers can simply declare something to be a certain way and it will effectively happen that way is a naive fallacy. And unfortunately bad ideas do not fail fast in the modern age due to a surplus of resources that allow them to keep going indefinitely.

Standard delusion or standard excuse? Often with authoritarians cruelty is the whole point.

I agree with you that on the broader society side, "something must be done; this is something; thus we must do it" is pretty pervasive.

Nobody views themselves as a bad person. If you want to understand actual motives, it is important to remember this. Your assertion is surely applicable to some sadist cops, but not to the average voter that gets riled up by the political/media establishment.