I don’t know if he killed himself out of penance for his mother’s crimes or loss of Margery, but he was the most moral of her children. The irony that she protected him from the destructive act and he still died is intense.
But what throws me off is that Cersei was getting dressed up in her fancy coronation duds before King Tommen jumped. Why? Did she anticipate a coronation as Queen or is wearing the same clothes just coincidence?