Plato's Opposition to the Myths of Homer and Hesiod

Plato's objections to the mythic, epic poetry of homer and hesiod did not stop him from composing some epic myths of his own. The fieto, the gorgius and the republic all include such a myth at or near their conclusion in the republic. So what was plato up to here? Was he trying to eliminate the competition, rubbishing other literary artists to make space for a new platonic philosophical artistry? There may be some truth in that. But there's more going on here than just artistic competition. To see why, we need to consider plato's objection to the poets and then look at what he tries to achieve in his own myths.