Their reasoning for it -you'll have to excuse Me, the narrator was talking over the scientists while they released it and My nihonjin is pretty rusty these days- was that after being blessed with the greatest experience of their professional careers, such a noble creature whose very existance made ours look quite puny by comparison should be allowed to return home and live out his life unhindered, as he was meant to be.
Reverence for ancestors (ancients and ancient things) runs quite strongly in the Far East.