It's simply too much and the middle part of the brisket wasn't going to cooked perfectly If the mid part is cooked, the fat is already too gooey And brisket is a roast, not a steak, so it's very chewy when undercooked (it should cooked until well done, not medium rare) The excess fat is still good for another cookout or homemade burger patty👌
Some people call it bark, and the others are saying its char or crust, it's from the burnt sugar, basically protecting the meat from burning 😂 And that's where the flavors are coming from🔥🔥🔥