According to Guns, Germs, and Steel, what factors involving agriculture determined why some societies end up as individualists and others...

Within Part Three of the book, Chapter 14 is the only one
that deals with issues of societal and political structure.  In that chapter, Diamond
describes four types of societies.  The lower two might be called collectivists while
the higher two might be called individualists.  (Diamond does not use these terms, but
we can infer them from what he says about these societal
types.

To Diamond, both bands and tribes are collectivist. 
He points out (for example in Table 14.1) that these are societies that are not
stratified.  He says that land is owned collectively in these types of societies, either
by the whole band (in bands) or by clans (in tribal societies).  Decision making is
egalitarian and there is no hierarchy in their settlements.  All of these things add up
to what we might call collectivism.

We must then ask what
factors having to do with agriculture determine which societies end up as bands and
tribes and which become larger.  Diamond says that any time a regional population is
large, it is likely to form a society of the larger two types.  He argues that
populations will become large whenever there are sufficient resources to allow for
relatively intensive agriculture.

Reading Chapter 14, then,
we can at least infer that the level of resources is what makes some societies
individualist and some collectivist.  A society like the Fayu, living in swamps where
agriculture is not even possible, becomes a society of bands.  A society like that of
Hawaii has many more resources and becomes a chiefdom.