Been thinking about if the Smoke Monster is just a manifestation of the Man In Black's hatred and evil, or if it existed beforehand.
I like to think the Smoke Monster is like Rover from The Prisoner - a tool or power meant to be used by the island/protector to act as a 'security system' to stop people messing with the heart of the island.
However, because of Jacob and the MIB being raised to be joint protectors, their powers were to be split between them - so when Jacob pushes him into the heart something goes wrong and he is trapped as the security system, while wanting to kill Jacob and destroy and escape the island.
So the original protective tool of the island actively works against the other protector, and seeks to destroy it all. When the cork is taken out, he is then disconnected from the source and can be killed, and the powers are returned to the protector like it was intended to be (for the first time in potentially thousands of years)


















