Bosnia and Herzegovina headed into its last day of World Cup qualifying needing Gibraltar to beat Greece—which would have been one of the biggest upsets in soccer history—in order to get into a playoff for a World Cup berth. It didn't happen, and Bosnia and Herzegovina's fans knew it wasn't going to happen, so they'd already began to deal with the bitter disappointment of missing a World Cup.
That put the Bosnia and Herzegovina fans in a foul mood, and they manifested their frustration by traveling to Estonia and throwing dozens of flares on the field during the game.