I know for a fact they went around due weather. They were number 2 behind the Lion Air aircraft. This comes direct from a mate in Virgin.
Surely if the aircraft in front of you crashes, you ought to be going around anyway? Although in this case it didn't, aiming to fly low over a crashed aircraft might give more problems if it burst into flames. You'd be without safety cover too, if they've all headed off to deal with the first one.