He was far too weak to possess someone and not be noticed in the goblin tribe and if you're talking about somewhere else besides the goblin tribe it wouldn't makes sense as there was no such place mentioned. If you're talking about in the simulation, that wouldn't work as you need to do the actions outside of the simulation for them to be effective. You could see this from when he got the rewards for killing the human, but not from killing all those goblins.

It never said anything about being detected due to his weakness. The goblin chief has a magic-related profession and that got him busted. How about the other tribes? Anyways doesn't he have multiple forms? Couldn't he just directly walk into the human city? Even after he got some enslaving mark he did not use it on the humans (at least not up the the chapter I read). He actually tortured them instead of just possessing them to get all their memories.... anyways, to me this story makes no sense as is.

They may no have had any useful information that he didn't already know, since they are not in such a high position as Anthony. If he were to change form and go to the human city, I doubt he would get any useful information as not even the guys with Anthony knew anything so I assume you need to get a high position. He could have possessed someone in the human city, but if he were to get found out and killed, he would permanently be dead as his soul was destroyed. As for putting an enslavement on Anthony, it could be easier to use him and discard him and it makes it easier to manage the tribes under him. And I doubt the goblin chief would have noticed he was possessing someone if he was stronger, since his skills also level up as he gets stronger so if his skills were better there could be a chance the goblin chief wouldn't have noticed him even with his profession.

Then try the new life simulation story Name Life Simulation: Rage Of Gods I know you wouldn't be disappointed