You being baffled is a you issue.
At least one juror wasn't convinced by most of the charges either, and they sat in the court room every day. I think it's safe to assume that it was the one juror who was the same hold-out juror for all of the majority verdicts.
The only 3 unanimous verdicts were for the insulin cases and for baby O, presumably because of the liver injury. I would bet that as that juror needed more to be convinced then the rest of the jurors that there's a high chance that juror is now questioning those 3 charges now too.
So if someone, a juror, sat in the courtroom every day and was only convinced by 3 of the 22 charges against her, why do you find it so baffling that other people may also not be convinced, especially considering all of the new experts coming out and disputing it.
As I said, you being baffled is a you issue. You say you're interested in human behaviour and psychology, why don't you examine what it is in YOU that means you can't accept other people can reach different conclusions than you?