The speaker of "Leda and the Swan" is like one of those news reporters who covers some natural catastrophe or burning building but doesn't step in to help out. He gives the play-by-play of Leda's plight while seeming to hover around her from all angles. His three separate rhetorical questions emphasize his curiosity about an encounter and a historical era that he can't quite wrap his head around.
In his defense, though, the speaker is narrating a story of which he already knows the end. He has hopped in his imaginary time machine in order to witness a momentous turning point in history: the conception of Helen of Troy. Even as the swan completes the sexual act, the speaker's mind races into the future to contemplate its meaning.