It's not supposed to be arbitrary, but there is no penalty if a prosecutor exercises it to favor his friends and punish his enemies - with a very narrow exception of blatant and totally off the wall charges. Loopy legal theories work.
The Waco biker cases are a good example. 170 people with boilerplate, non-specific indictments. Challenegd in state and federal courts, all upheld. see too, January 6 political prisoners. All upheld by courts.
it is an incredible amount of power. It can be abused without penalty. The recourse, accourding to the rule of law, is throw the bum out. That remedy doesn't work in a banana republic.
It's pretty much if you are in that regime's sights, you're screwed. There is no remedy at law.
No remedy at law for government lying by insinuation "Russia, Russia, Russia" either.
This is why George Soros spent so much money getting his preferred DAs elected all over this country. And why we must find a way to counteract his money and power and get honest DAs in those positions.
Well...there is one other remaining option.