I get that your question is
"WHY was it random?" and the answer, though I'm not an official, is because they wanted it to be.
But why did they want it to be? They must tell me!
No, they have no obligation to tell you anything ever and furthermore the answer would make no difference at all.
But then I would know why I got the shaft.
Because it was random.
But why was it random?
Because they wanted it to be.
But why don't they tell us why they wanted it to be?
Because they have no obligation to tell you anything ever and furthermore the answer would make no difference at all.
You can see how this can go on for all of time.
They either have a reason or don't and either way it makes no difference because it happened, it was random and most importantly it happened and was random.