Helter Skelter has been strongly called into question in recent years. While Manson was for sure nuts, so was the prosecutor Bugliosi. The dude just made shit up and lied and concealed facts to present a tighter narrative and get himself fame with such a big wild case.
This book sheds a lot of light on the real complexity of the Manson case, and makes it pretty clear that the Helter Skelter motive was basically whole cloth nonsense made up by the prosecutor.
" Author and investigator Tom O’Neill has shed uncomfortable light on the Tenerelli case in a chapter of his new book “Chaos: Charles Manson, the CIA and the Secret History of the Sixties” – a 550-page profound dive, 20 years in the making, into the plethora of inconsistencies and glaring holes punctuating the formal Manson narratives to date "