It is rarely, if ever, possible for a single proposition to serve as a complete and adequate explanation of anything. In history, literature, the sciences, or any other discipline, an explanation can involve a highly complex set of propositions.
Explanations are diagrammed in the same way that arguments are. The parts of an explanation can explain the explanandum either independently or jointly. Explanations can have more than one step; in fact, most of them do. Finally, a single hypothesis can support more than one explanandum.
There are two basic questions to ask about an explanation.
First, is it adequate--would the hypothesis, if true, provide a genuine explanation of the explanandum? Does it provide a possible cause or reason, or in some way fit the explanandum into a wider context that makes it intelligible? A good explanation is one in which the explanandum follows from the hypothesis; the relation between them is such that if the hypothesis is true, the explanandum has to be true as well--or at least highly likely.
Second, is the hypothesis true? False premises don't prove anything, and false hypotheses don't explain anything.