Judging from the way that China handled the outbreak it was either an accident or it was what the scientists claim: people eating exotic meat.
I tend toward the accident theory. There is a large number of truly arrogant scientists in the world ... scientist who would collect dangerous viruses without adequate precautions.
A more interesting question is: Why was the world response to this outbreak so heavy handed?
I doubt the world will ever know the true cause of the disease. However, the government response to the outbreak is public. That is the thing that we should scrutinize.