Why was Robinson Crusoe so important at the time of its publication?

Another
innovative feature to Defoe's is the candid introspection of the narrator.
For, before the publication of this novel, there were few characters who internalized to the
extent of Defoe's main character. Frequently, Crusoe expresses his doubts, regrets,
and examinations of conscience. For instance, in Chapter II Crusoe reflects upon his father's
advice, 

At this surprising change of my circumstances,
from a merchant to a miserable slave, I was perfectly overwhelmed; and now I looked back upon my
father's prophetic discourse to me.... [and] I thought was now so effectually brought to pass
that I could not be worse; for now the hand of Heaven had overtaken me, and I was undone without
redemption....

In Chapter VI, also, he attempts
to "describe the horrors of my soul at this terrible vision," his dream about the
wreckage of the ship on which so many perished.

While a precusor to the
English novel, Robinson Crusoe is also, as...