I don't know for sure, we only covered the basics in school so I don't know the exact reason.  My best guess though, bodies sometimes leak fluids even after being embalmed so funeral directors will put them in a unionall (basically plastic footie pajamas).  For a little extra insurance they might also put some absorbent powder in too, which is usually perfumed.  So I think it probably ended up being decomposition smell over-powering and mixing with the perfume to create a wonderfully appetizing fatty smell.