Hullo Fourthdaughter, Finding the reasons why people do things can only come from personal papers, letters, etc. Online resources dont cover reasons.
Your grandmothers death certificate along with those other members of family will have cause of death. Some will have length of illness and treating doctor, if it was in a hospital those records are available to immediate provable family.
You can purchase the DC's or transcripts of those which are cheaper.
As you find out more about each family member you can start to put a picture together. Most people move for Work or family reasons, sometimes housing comes into play. Look at the times and what was happening both where they lived and where they went to. Quite often people moved to a location on the recomendation of others, this can be government schemes or private friendships/family. Good Luck in your search.
Happy Christmas
Neil
