The second commandment is the command for us to properly worship one God. When one surveys history there are many nations that have served many gods. Why do we want to worship one God? Why would we want to put all of our eggs and hopes in this one basket?
There is a famous statement that you do not want to put all your eggs in one basket. The point is that if you drop that basket it breaks all the eggs leaving you with nothing. So, it is wiser to distribute your wealth across different baskets. If this is true then why worship one God? It would seem to make sense to worship a variety of gods to cover all basis? Why is it wise to worship one God and live your life in light of HIs promises?