As I noted above, it’s well documented Manson befriended Dennis Wilson in hopes of help in getting a recording contract.
As an aside, Terry Melcher (son of Doris Day) had been living in the Tate home previously. Perhaps Manson was exacting revenge on Melcher refusing to give him a recording contract.
Living in Hollywood at the time, I still recall the massive Police presence for days in the Hills.
The gang cut the telephone wires; well before the age of the cell phone. There was a lot of debate over the knowledge of the live-in caretaker, who lived in a small building adjacent to the Tate home. He always disclaimed knowledge of what had happened while it was happening. Knowing these goofballs, it is surprising they didn’t go into his dwelling as well.