Alive troops return to base after attack
When townhall sniping was removed supercell said they did it cause in reality nobody would keep the heart of the village out of the village. Also now when the clan castle troops are in a poison spell they move out of it cause in reality nobody would just stand there inside a poisoned area they would obviously move out of it.
So similarly when the troops win an war. They return back. In reality too they obviously return. Not that they died on their way back. Supercell if reality matters so much to you then you won't have any problem doing this.