I actually went a bit through the book again and this is discussed, at length, in the book. The state security services explain (as if they would ever explain that in reality) that going after innocent people is a feature, not a bug. They're going after supposedly disloyal people just to put the fear in everyone, despite knowing perfectly well that these people aren't actually disloyal. That they know perfectly well the accusations they make are false.

The accusations are not the point. Well, occasionally there are actual criminals where it is the point but in the 99% case is isn't the point.