Ground crew fueled it with, say 500 liters instead of 500 gallons. It's happened before.
Judging by the picture of the resulting fire after the crash, the fuel level was down to the tank standpipes. Appears there was only about 10 gallons of fuel left in the tanks. Similar to the Korean Air Heavy that crashed at SFO a few years ago, both engines were ripped off and no fire when they hit the rockwall.. They ran out of fuel on final approach and couldn’t maintain the glide slope on short final. No fire, no fuel when the center tank is ripped open and engines are taken off.