Bruce Wayne: Died in a Rasputinian way, saving a drowning child while disarming a nuke and redeeming a villain at the same time. Damian Wayne: Died because all of the food was on a shelf he was too short to reach.
bruce wayne died because now that alfred's gone he went into the kitchen for the first time in his life, tried to pick up a can of peaches to cook dinner with, ended up triggering one of alfred's mouse traps and it killed him instantly
tbh i do actually think bruce's character arc ending in him dying of something completely normal like cancer is probably the route i would go for him if i were writing DC comics.