I don't think that the defence had to prove CI, just show that it was a possible explanation, sufficient for the jury to have reasonable doubt that the charges against AH were untrue. The burden of proof is for the prosecution to show that manslaughter and endangering an aircraft took place. The prosecution failed to show that convincingly to the jury.
This was an adversarial event not an inquiry. In my opinion AH did not win so much as the prosecution lost. I don't think that the prosecution could have shown that CI did not occur. He has been found not guilty of the specific charges brought against him. However, he has to live with the event and the deaths in which he was involved.