This misreads Hume. Hume is not a radical individualist--quite unlike Hobbes,
who really does give us a world of atomic of atomic individuals bound
together only by contract. Hume's metaphysics is a mosaic of events that
merely happen together, but his social philosophy is genuinely social. Look
at his account of justice, where he makes fun of the very idea of a social
contract, and explains justice instead as a functional convention arising
from the needs of people for mutual accommodation given their
interdependence. The implications Hume drew from this were cionservative
rather than radical--Hume is a Burkean liberal who thinks we oughtn't go
around radically disturbing the conventions that have arisen, but he favors
English liberty as it existed, more less, in his day, as a successful set of
conventions.
There's no particular reason to expect one's ontology and one's social
philosophy to mirror one another--only a premodern "great chain of being"
metaphysics would lead you to think that the structure of events as such
would be in any way like the structure of human relationships. So a "mosaic"
metaphysics doesn't imply an individualist social philosophy--or indeed, vice
versa. Hobbes was a strong believe in natural necessity and opposed the
corpuscularian new philosophy of Boyle and Newton.
--jks