The Essence Soul realm was a realm where one create an Essence Soul and grew it alongside them. They were both separate enough in that realm, and the Essence Soul even had intelligence. But it was little, and always overshadowed by the normal intelligence of the body, so it never showed up when the person was alive.
However, when the body died and the Essence Soul remained behind, it finally had its own intelligence to control itself. And the intelligence it had was way too little to tell anything.
Most Essence Souls were confused when they appeared. After all, they had no idea why they could even think. The body did it for them all the times before.
However, now that they could, they knew that the body was gone. If the body was gone, it had died, and death frightened it. It had no intelligence to tell how it had even died, so all it could assume was something bad had happened.