Morgan was puzzled, and he wasn't the only one. The others had the same thought process as Morgan and ended up concluding that Lin Yun probably hadn't been the one to kill them.
After all, in the Abyss, strength was directly related to the Demon they had reincarnated as. Whether they were powerful or weak depended on their Demonic Bloodline. Although this wasn't absolute, it was the most important factor.
Since Lin Yun helped Slythrin protect his body, that meant that he definitely didn't care about their previous grudge, or at the very least, he took the big picture into consideration. Birbo and the others had to have died in the Abyss due to terrible luck.
Clombton occasionally looked at Lin Yun with an admiring gaze, and even Cross felt that Lin Yun was a lot more pleasing to the eyes.
No one doubted Lin Yun aside from Slythrin, who knew the truth, but he stayed hidden within the group.