What is the significance of Magwitch's death? Why did Dickens have him die, but not hanged as he was sentenced?

I think Magwitch's death was a major turning point for Pip. It is here when Pip's expectations come full circle. Pip begins to see life and humanity for what it is. Pip sees beauty in a criminal and ugliness in gentlemen. THere is a certain natural progression of life by having Magwitch die without execution. It is a progression that neatly leads into Pip's progression.