The bandits didn't really have martial arts skills and they were merely using brute forces when robbing. They quickly attacked Yao Ying's party without mercy. Despite being weak, Yao Ying and Lin Jian were still able to retaliate and they had the advantage of using their inner qi to help them fight.
It made their condition wasn't too bad and in turn, it made the bandits feel annoyed because their mission went awry. They thought that they would be able to swiftly kill all of them while they were sleeping.
The bandit leader could see that one by one, his subordinate started to lose and they were killed mercilessly. On the other hand, their target didn't have any casualties --- except for those two people that they killed because they fell asleep while guarding the camp. It seemed like they picked the wrong target this time.