The root of the word "siloviki" is "sila", which means "force". And it is about using force in order to perform their job. Like policemen do. Or security guards. Or soldiers.

And it is not used to refer to crime activities. They also use force, but they are not "siloviki".

As does "Department of Homeland Security". That was the first federal agency named that way, and prior to that people would have thought that sort of naming to be associated with the Stassi or a totalitarian regime. I suppose it is commonplace now.

nope. the 2nd word means "structures" and it implies part of the state.

No, that sounds like any armed forces, police force, the secret service, etc.