Why did "God" "create" the world?

A friend of mine asked me this question on Facebook recently: So why did Krishna create this universe? Is it for fun or is there a purpose/goal to achieve something..?
Good question. Glad someone is even pondering. That I think is the first thing that makes us human. Consciousness.
First of all I do want to replace the word "Krishna" (proper noun) with the word "God" (common noun) to attempt an answer.
Its an interesting loaded question though. To answer that question, you have to first understand what/who "God" really is. And what "creation" really is. Its an important point to clarify before we attempt to answer the main question. My answer is based on my understanding of Advaita, mixed with the more common more popular notion of God.

The Vedas are very clear: Where your thought and language cease to being able to imagine or explain, the Almighty (God), is 10's of hundreds of times larger than that.
i.e. God is infinite.

Talking in terms of the common notion of God:
Knowing what science tells us today about the Cosmos, its size and the possibility of multiple universes, that science can only theorize but not prove, does very much confirm the above statement about the "size" of the divine.
Having said that, when the mind, thought and language have stopped and are incapable of explaining or understanding the diving with intellect, can we then, attribute this question of having a purpose for creation? Its a very difficult thing to understand. I think the question itself is meaningless, because we assume that the "creator" needs a "purpose" because we think that this creator has the motivations of us humans or for that matter animals. It is natural for us to think that there might be a purpose because that is how living being with a mind think. Everything is about a purpose. Everything we do is for some purpose that satiates and lights up some part of the human brain.
But the infinite God, in all probability is not motivated by purposes. Its an absurd proposition to think otherwise.

Talking in terms of Advaita:
According to Advaita, the ONLY thing that is reality is the Brahman/ the super consciousness (call it what you want, Brahman is the name given by Adi Sankaracharya), . Everything else is an illusion, in fact there is no everything else. The fact that we think there is something else is an illusion. (science seems to think so for sure, look up "super string theory", along with what is written in the "Fabric of the Cosmos").
Now, having defined "God" in the context of Advaita:
Lets us examine what Swami Vivekananda (because he himself was the student of Ramakrishna Paramahansa who was a advaita guru and a "self-realized"/ "god-realized" (again, call it what you want) man) had to say about this idea of creation:
"Here it may be said that these laws as laws may be
without end, but they must have had a beginning. The
Vedas teach us that creation is without beginning or
end. Science is said to have proved that the sum total
of cosmic energy is always the same. Then, if there
was a time when nothing existed, where was all this
manifested energy? Some say it was in a potential form
in God. In that case God is sometimes potential and
sometimes kinetic, which would make Him mutable.
Everything mutable is a compound and everything
compound must undergo that change which is called
destruction. So God would die, which is absurd.
Therefore, there never was a time when there was no
creation."

As it is obvious above, there never was a time there was no creation. Creation is without beginning or end. So again, this infinite Brahman, doesn’t think the way we do. It is erroneous on our part to attribute the need for a purpose for creation.
Swami Vivekananda does, in the same speech talk about, how this “self” which is not devoid of the Brahman go into an illusion and think it is different. And the answer is: We don’t know.

But I ask you this: How does it matter the purpose of creation? There might be, there might not be or the question itself could be meaningless when attributed to the infinite. What is important though is to understand your purpose.
The same Rishis’s that found out the most fundamental aspects of the universe (understand, universe and creation, are in my view two completely different things), like its age, the fact that it is without beginning nor end. Facts that modern science is just coming to terms with after spending billions of dollars on equipment, have give humans what their purpose is. And that purpose is to “reach” God/”realize” God/”attain Nirvana” (again… call it what you want.). But according to Advaita the day you realize, that this world is a complete illusion, not intellectually, but spiritually, you will have become one with “God”, one with the infinite. And reaching that state is your purpose. 

I think I will stop this blog post here. Because this can become too long.

Of course do leave me questions, these are complicated topics in my view, and I will answer them to the best of my ability. Or at least point you toward a better more scholarly source.