[quote]The Stars would've obliterated the Flood[/quote]And destroy resources, and bring about the extinction of millions of species. The speed at which the Flood spread means you need to cause the sun to go supernova as soon as they arrive in system so they don't grab a new ship and leave with more Flood. Additionally, what happens when the Flood detect this strategy? All they'd need to do is jump past the stars and exit slipspace at core Forerunner worlds, or the Capitol itself. Then what? Or what happens when the Precursor architecture begins reactivating and join the Flood ranks? It's an effective strategy, but not one they can use short term or on a large scale.