(1) Questions like yours also interest and confuse me.
(2) According to one excellent book (A Comprehensive Grammar of
the English Language):
He died of hunger. (cause)
He died from exposure. (means)
(3) My daily newspaper is considered one of the top 4 newspapers in the
United States. Every day I check the obituaries (death notices) to see
what prepositions are used. I have found that most (not all) writers say:
She died from the complications of cancer.
(4) I found these examples in Webster's New International Dictionary
2nd Edition Unabridged (1959):
die of old age
die by another's hand [murdered]
die in poverty
a plant dies from lack of care
(5) I found these in Funk & Wagnalls New Standard Dictionary of the
English Language (1958):
die of fever
die by violence
die for one's country
die in agony
die to the world [NOTE: this means, I think, that some very religious people do not do the things that most people do. That is, they pay attention only to religious matters -- not to the usual things that interest most people in this world/life.]