The two Earth Overturning Great monsters were focused on keeping Count Falgur away from the injured monsters as he was the only person present here who was capable of killing it.
For that reason, they were not paying much attention to anything else. Specially someone giving off the aura of a weak low level knight was not a big deal at all.
Even in its injured state, the Earth Overturning Great monster should be able to take care of something minor like that without any problem.
Weiss took advantage of this situation and got closer to the monster who was currently weakly lying on the ground trying to recover as much as it could. With its current weakened state even going under the ground was not possible.
It was able to sense Weiss getting closer and casually sent a tail bash toward her. This simple attack was more that strong enough to put most low level knights in fatal danger.
