Any reader of Dickens will know that he often relies on rather incredible leaps of the imagination to make us believe the stories he is writing. Often critics have judged Dickens very harshly for his reliance on the amazing power of coincidence. In this novel, one of the biggest elements of coincidence is when the Artful Dodger just happens to steal from Mr. Brownlow, who in turn just happens to be a relative of Oliver and a very kind and gentle man who implicitly trusts a character such as Oliver, who most people would have handed over to the authorities. Examining such events from this viewpoint, we can clearly see that so much of the plot relies centrally on coincidence.
However, it is a mark of the skill of Dickens that he is such a compelling storyteller that we often choose to overlook such leaps of the imagination and just settle into enjoying the story. We willingly partake in what is called "the suspension of disbelief" as we basically enjoy the story so much that we accept such coincidences without questioning them. In a sense, another way of looking at these coincidences would be to say that, actually, life is made up of such coincidences, and so perhaps it could be considered realistic that they are such key elements in these stories that do so much to reflect life.