Local organized crime leaders had no more disdain for law than most policemen, prosecutors, judges or politicians. However, due to the nature of their activity, they had to maintain a reputation of honesty and reliability.
People feared them, but they were generally true to their word. If you paid the protection tax, your shop was protected. Of course, the tax could be raised without any advance notice, but more astute negotiators generally managed to delay enforcement by a few weeks. But your shop was fine.
Policemen, on the other hand, did nothing of that sort. Even when not actively assisting the crooks, there was no proactive protection of any kind. The police could only step in after your shop was devastated for the first time -- and even then, the usual process was that you'd file a complaint and, after the legally-required 30 days, the local police would send you a short letter saying they couldn't do anything due to lack of evidence. Assuming, that is, that the post office didn't lose the letter.
Law enforcement agents were seen as very unreliable partners: sometimes they'd help civilians, sometimes they'd just stay out of it, and oftentimes they'd blatantly and obviously take the side of the mobster who was paying them to look the other way.
The crooks, on the other hand, were seen as reliable. Yes, they were ruthless, but you could generally count on their help, if you were willing to pay the price.