Hosea always seemed like a father figure to me. We know that Dutch and Hosea both raised Arthur and John after picking them off the streets, but I think Hosea is more of a father figure to them than Dutch ever was.
Dutch a textbook narcissist so you could say he never really cared about Arthur or John. But I'm guessing Hosea was the one who taught them most of the things they know.
He was also the only thing keeping Dutch from going off the edge and the boys knew that. After he died, everything just went to shit a lot faster.
You can tell Dutch doesn't like taking anybody else's opinion into account since he has this extremely exaggerated sense of self importance. Hosea was the only person who he thought was even close to him on an intellectual level. He was the camps voice of reason.
