I love this drawing and the message of this drawing! To me I think that the message is basically is people that did not have faith, so when they perished and became rotten of flesh and bone, they realized that if they would have faith in the first start when they were alive, they would have been blessed. That is what I think the message is.
To me it looks more like people struggling to find a reason for their suffering, pleading with their god to make it stop, unable to comprehend that there is no reason, no great plan, no god to plead with.
That their suffering is pointless, their lives insignificant, that if anything is out there that can help them, it certainly isn't listening.