There never was a Zodiac Killer. There were a series of unsolved murders in California. Some kook (probably a cop or reporter or someone with access to crime files) wrote the letters because he was an attention whore. The murders which are considered the work of the Zodiac, were the work of 3 or 4 different shithead killers. ZOdiac just claimed responsibility.
Manson was a pimp and a pettty criminal, but his real calling was pimping and music. He turned a bunch of hippies out to hang out with Dennis Wilson and record producers, score drugs, bang them himself, and get a recording contract. Charlie loved attention. The Tate-LaBianca murders were drug related—more to do with Tex Watson and biker gangs than Charlie and Helter Skelter. But once the cameras were on, Charlie basked in the glow of the light and turned his crazy up to 11.
The news sells fear. The news in the 60s sold Hippie Boogyman fear with Charlie and the Zodiac. They're myths