Rumours
Mach, they don't target at random. It is rumoured that it is when one disagrees with them, or worse, makes a complaint about one of them to the ICC or takes them on in the AAT that is when one is 'marked for execution' generally.
Why do cowboys robustly dodge regulatory scrutiny? Well again it is rumoured that often when the cowboy does receive a regulatory pineapple he simply bends over and compliantly takes said pineapple - no fuss, no complaint, life goes on. As long as said cowboy doesn't do anything that tarnishes the reputation of a regulator, impedes a regulators promotion by making a complaint to the ICC or action in the AAT, and does not cause the Regulator to come under a spotlight, life goes on.
And again the rumour is that some backyard operators (and some bigger players) have 'mates' inside the regulator (aviation is a small incestuous industry) and again this allegedly explains why some operators are left pretty much unscathed.
The biggest liability is an operators mouth when they attempt to expose an alleged miscarriage of justice, complain about unfair treatment including threats, intimidation and bullying. Best to roll over and take it like a man unless you wish to end up sitting in a star chamber beneath a bright spotlight.