Kimi really impress when he started the race with hard tyres and managed to leapfrog the BMW and Renault during first pitstop.

Usually the team orders (not directly of course) their drivers to stop racing each other after their last pitstop. Maybe it's why Kimi didn't overtake Massa eventhough he's on soft tyres. Or maybe it's the dirty air from Massa's car that prevents Kimi from staying close to him before the main straight.