Nugget's situation in kg1 is actually really sad when you think about it. He is a 5-year-old who lost his only friend, and does not know what to do and how to deal with the grief. And how would he? He is 5 years old.
I know Nugget is our chaos creator, brings the apocalypse three different times and there are a lot of theories about what he really is and how much he knows, but in the end of the day he is a little child, like all the kids. He is a little child who lost the only person he was close to, and has no one else, because the other kids are avoiding him and the adults are the real danger. The shrine he made for Billy, while it is macabre af, is really so sad. He is really just a child who is trying to deal with his grief.