When Kizaru attacked Supernovas at Sabaody Archipelago, he beat some of them badly like X Drake, Basil Hawkins, Urouge and Scratchmen Appo. My question is: how did they manage to escape from Kizaru? In episodes, the scene ends with the (temporary) annihilation of the Straw Hats. But how did they manage to escape? Is it because of the Navy's carelessness?
Lets first see what happens on Sabaody Archipelago.
Chapter 508 Kizaru arrives on the island, searching for Sentoumaru. Since he couldn't find Sentoumaru straight away, he gets bored and when Kizaru is bored, he
Couldn't possibly just leave a bounty head like this sitting around...
So that's why he started attacking the super novas in the first place. He didn't really intend to do so otherwise. He wasn't ordered to do so and had bigger fish to fry.
Chapter 510 Kizaru finally contacts Sentoumaru and goes after the Strawhats.
Chapter 511 Kizaru finally meets with the Straw Hats, but is kept busy by Rayleigh.
So to summarize. They got away, because Kizaru never told the Marines about the supernova's presence. The Marines didn't know about their presence so they never ordered Kizaru to arrest them. He only attacked them, because he was bored anyway. I think he really only does what he is ordered to. He and Kuzan are the lazy type like that. Secondly, Rayleigh kept him busy for some time, giving them time to escape.
Simply put, Kizaru wasn't there to arrest the supernovas. He was there to execute or arrest the Strawhats, or more precisely, Luffy, since he broke the law and assaulted a Celestrial dragon. That was his primary objective. He could have arrested them but that would have wasted time and the Strawhats would have escaped. That's why he concentrated more on them.
The reason he attacked the supernovas was because he was bored and it did not take much effort, while arresting them would.
You could say that the other marines should have arrested them as they were injured anyway, but the low rank marines are still no good against the supernovas. And hence, the supernovas were able to escape.