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What prevents attaching it to a trigger for a new day?
After all, if the enemy town remains without a hero and is captured, your trigger (Trigger (PLAYER_REMOVE_HERO_TRIGGER,PLAYER_4,'lost_PL4')) will not work.
regarding the trigger - yes, but if you have 4 players, and only one of them dies, and a hero is needed - that's why a loop is used instead of a trigger.