Why does the Hand think that the Black Sky is an empty vessel?

Question

The Hand is well-known for using resurrection to maintain both their own immortality and that of others. As we see on Iron Fist, it can lead to the person it is used on becoming more and more violent and disconnected from their previous self, but they still seem to maintain their general memories and personality. The leaders of the Hand have been using this process for millennia.

However, in The Defenders, both the leaders of the Hand and

Stick believe that Elektra is gone, and that she is an entirely new person as the Black Sky.

They later turn out to be rather mistaken: Elektra seems to recall most of her previous life, as indicated by her conversations with Daredevil, though it’s not clear that this was initially the case. Still, it’s not a surprise that she had some initial disorientation: we saw that in Iron Fist too.

Why would the Hand believe that her memories are gone due to resurrection, when the process doesn’t seem to work that way for anyone else?

Answer 1

Black Sky is not the Hands plan it is solely Alexandrias as shown on a more then one occasion. The other 4 members of the hand accuse her of acting unilaterally in using up there resources to make Black Sky. In addition I think it is Murakami who tells Alexandra "Black Sky was always your obsession not ours" or words to that effect. It is also clear that rest of the Hand leadership do not trust Black Sky

The other thing to remember is that Black Sky is not of Kun Lun so the hand discovered the myth after being exiled back to earth. Possibly at the same time they taught themselves how to defeat death using there "Resource" and the way the hand revere Black Sky suggests that Elektra may be the first time they have actually made one this doesnt mean she is the first, as if the myth of Black Sky was learnt on earth it is highly likely one was created by someone other then the Hand. It is also possible that until now any Black Sky that has been created was a child (As Elektra should have been, and the child that Stick killed was). Thus Black Sky in that case could be raised and manipulated into being the weapon of the Hand.

All this means that Alexandra has created something she thinks she understands and can control but really has no idea how it works she treats Black Sky like a child when the body she resurrected was an adult.