The Fantasy Goblin BOSS' Illusion Spell was very scary and had extraordinary range. The entire Middle Street of players were under his Illusion Spell.
Middle Street was already crowded with people and with more Thorn City's players swarming in, more players were under the Illusion Spell so there were more and more "monsters" on the street.
It was an anarchic situation and in one look, the entire city was filled with monsters that were afraid and excited.
Although the BOSS was at the centre, most prominent location, everyone understood the logic of having to kill the smaller monsters before killing the BOSS, much less since they were Fantasy Goblin. If they killed them, they would drop fragments… So long as they killed one before dying, they would have earned enough.