That is the same rationale for all of the other hearsay exceptions, e.g. statement against interest. The idea is that nobody would say something that incriminates himself unless it was true. However, if it is testimonial, confrontation is required. Your rationale that the statement is reliable, so no need for cross-examination, is the same rationale that Crawford rejected from Ohio v. Roberts.
I’m still not seeing why a dying declaration, under the circumstances given in the OP, is not covered under Crawford.
Don’t know the answers to all your questions, but NBC Washington’s coverage of the trial noted “A man who said he planned the robbery with Hailes identified him in court Wednesday as the shooter. He said he did not want to appear in court because he was afraid.”
I don’t know if it makes a legal difference but for me it makes a moral one.
Did the prosecution let the defense know they had this dying statement for the two years he was still alive?
Did the defendant know he was being investigated or charged for the death in the two years he was still alive?