Answer:
Atticus says that Bob Ewell must be crazy to attack Jem and scout, it is the only explanation he could think of that will justify a man to attack innocent children.
Heck Tate disagrees and says Bob Ewell was just mean and had enough liquor in him to make him brave enough to attack children, implying that he was a coward.
Of the two, Heck Tate's explanation is the most correct and the one that aligns with how I feel about Bob Ewell.
Explanation:
Atticus cannot understand what could possibly make a man want to kill children unless the man is mad, so he says Bob Ewell was crazy.
Heck Tate however, assures him that Bob Ewell was not crazy but just "mean as hell" and a coward on top of that, so his attack on the children was inevitable.
Heck Tate's explanation is the correct one.