Well to answer the question,the people had set up a golden calf to treplace God. God had gotten angry cause they were dancing and praising this useless idol and Moses was upset but pleaded for mercy for the nations and future generations. God does get angry when we rebel but once we repent then his anger is only for a short time. if we do notor we are naive in our hearts then God's punishment will come on an unrepented heart like whn Mose threw the tablets and the land broke and fire poured out swallowing the unrepentant and disobedient people