do you believe that it doesn't matter who did it?
The end result is what we see, so something happened. Who did it is certainly and open question.
I believe I know who did it and that person or entity (probably a better word) is the Creator, IMHO, GOD.
do you believe that it could have been green aliens?
No.
do you believe that it could have been many designers?
No I don't. But I do have a reason for that belief, one that I must admit is based on personal experience and could well be flawed.
My general experience of design by committee has not been good. Unless there was one overriding mind, one clear concept of what was to be, I don't think we would see the consistency throughout the universe that seems to be apparent. If it was multiple designers I wouold expect to see greater variation at the most basic level, that some of the designers might have seen gravity as a repeller as opposed to attractor.
Aslan is not a Tame Lion