He took his team mate and Alonso out the race. The safety car gave him a huge advantage. Schumacher and Webber were both on older tires. So they had less grip than him and strayed off line. Then Vettel made a mistake. Practically giving Jenson the victory on a plate. Both Alonso and Hamilton were about to over-take Button before he took them both out. So either one of them could have won the race.
Button was also helped by Heidfeld retiring, Massa losing his front wing.Then the safety car played a massive role in keeping the pack together, helping Button.
If Webber, Alonso , Vettel or Lewis had won this way, everyone would say they got lucky. But as always Button has the media on his side, and people always over-look how lucky he gets sometimes. The reason why??? English bias. Only due to all of the things above did Button win.