He wasn't convicted because the prosecution couldn't find a witness that could testify they saw Lewis stabbing the victim. But there were plenty of witnesses who verified that Lewis was present. Plus, they had him on obstruction of justice, aiding and abetting, and probably accessory to murder.
Ultimately, the prosecutors gave Ray a deal he couldn't refuse.
"It's a lot easier being a drug dealer than an AAU coach" - this guy. Tell me something I don't know. I mean, don't think but have never tried either.