Did God only care about Israel before Jesus came?

Most of the Old Testament centres on the history of one nation -- Israel -- to the extent that they become known as God's chosen people.  We read how God saved them from severe famine, freed them from slavery, led them into a new land and gave them victories in battles over and over again.  God made a covenant with them and declared His love for this people without reservation.  They were special.

The curious fact is that God made all of mankind yet seemed to just favour one nation over everyone else.  Why?

In Isaiah 43:12 we read that God intended to have Israel be His witness.  Witness to what?  Apparently to the fact that He is the only true God.  We know that other people groups were worshipping many gods in those days.  In choosing and then leading Israel God taught the Israelites to serve Him alone.  As a result, they gained notoriety far and wide for their allegiance to the one God -- Yahweh.  And a number of Israel's leaders and heroes clearly grasped God's purpose in this -- for example, the author of Psalm 67 who expresses his desire to make God's ways known all over the earth and that salvation would be among all nations.

If we know to look for it, we see evidence that all nations were included in God's plan in the Old Testament.  Gentiles were never an after thought.