What are the other two factors besides micro-tears of muscle fibers? Is it the production of human growth hormone and decrease of myostatin as a result of the increased human growth hormone. Is it the supply of glycogen into the muscles to make them appear bigger?
I'm not a scientist as you can tell, but I would imagine that the primary goal of muscle growth is to tear the muscles than build it all other factors would aid in that process.
You tear a muscle then the right nutrients/materials have to get to the muscle to repair it, then you have to make sure that the muscle is not used for fuel.