I think people who 'ghost' may have communication issues, they do not know how to convey their true feelings, so hence become an ostrich burying their head in the sand hoping it will just go away and not have to face the problem they cannot handle. It is their coping method, how they deal with stressful situations.
I know when my daughter died, suddenly lots of friends and family just disappeared from my life. When I confronted them about it a yr or so later many admitted they did not know what to say to me. I explained that they should have said just that!
They also said they did not want to upset me with their personal grief. So many people cannot handle bereavement and now I just accept people deal with death in their own personal way, no one is right or wrong, you just have to do what is right for you. Also your bereavement affects others around you as they had some form of relationship attachment to the person, they are grieving too but may not wish to burden you further with the weight of their own grief.