I'm not commenting specifically on O. J. Simpson (or Michael Jackson), but making a point about criminal trials. A conviction in a criminal trial requires proof beyond a reasonable doubt. A court may acquit due to reasonable doubt in the face of strong circumstantial evidence for guilt. An outsider might still reasonably conclude the defendant had probably committed the crime. The
jury might conclude, based on the evidence, that the suspect had most likely committed the crime, but properly reach a not guilty verdict, because there is reasonable doubt.
According to those whose conclusions on the subject truly matter
They matter in determining the verdict and the defendant's fate, but they operate within the processes of the legal system, which has a slightly tangential goal than to reach a definitive statement of fact over what actually happened.
(Again, I am not prepared nor have the desire to enter an argument about O. J. Simpson's or Michael Jackson's actual guilt.)