Moe was mad about HKS accepting money from ET to cover the funeral - especially the ceiling cam in the church.
Well, it has leaked out they had a big falling out after the funeral, so I can imagine that Moe, who made a point of traveling with ANS from the morgue to the airport to the church was stunned to walk in and find HKS had turned it into a circus. Who know, he may have disliked the statement HKS made at the funeral as well... but HKS's greed may have done him in if Moe spills all he knows.