"indeed they did. but history can be careless about who it remembers" is this a simile or an idiom or a personification? why?

What is the significance of the above statement in relation to the play’s conclusion? oedipus treats his inferiors poorly but ultimately grants them the same respect he grants to nobility. while teiresias appears to be mocking oedipus, the real message is one of warning about the forces working against the king. oedipus earns great fame for answering the riddle of the sphinx but ultimately loses his crown to a common man. just as oedipus is unable to conceive that he has done wrong in the past, he is unable to imagine that his enviable position is impermanent.