The reason the shark was so large is because it was pregnant. Great Whites and other Sharks are not aggressive when they are pregnant.The reason the divers got so close to the Great White is also because it was not feeding. If it was feeding they would possibly be dead.
I think that the divers should of went down there because they got some killer footage and the Shark was possibly one of the largest Great White. However if I was one of the divers I wouldn't go down there!