>>283609041
I'm not implying their mimicry is perfect. I'm saying It is unreasonably advanced for something that barely has any use.
Generally the idea that monsters have huge mana pools and overwhelming fire power yet resort to underhanded tactics for no reason other than just because makes very little sense. Like an average demon even if it looked and sounded nothing like a human could enter any human village at night and erase it from the face of the earth.
With such creatures roaming around human race had no hopes of surviving, and the creature capable of pulling this off had no reason to pivot into developing any other tools to secure its niche.
The link between mimicry and intelligence is also a far fetched one. We have fucking plants in real life use the tactic. Clearly there's a pretty big gap between being able to imitate sounds and developing a rational mind.
Now the advent of the demon king as the origin of demon society only makes sense retroactively, and even then the narrative still contradicts it as the demons still do not care for their young.
If the demon king is an outlier, the rest of the demons have no business having such large mana pools since there were no evolutionary pressure for it to that to happen given that their prey is weaker than them and they led a solitary lifestyle.
Them grouping up to become a bigger threat makes sense from the stand point of a conquering sovereign nation, but not from a stand point of survival. I'd recon demon king would find it difficult to roam around, gather and keep on a tight leash all of the demons living who knows how many kilometers apart from each other. They have no instinctual need for a community neither for safety reasons nor for the reasons of food procurement.