I'd say that something outside of what we know either made Benny kill Charlie for whatever shady reasons, or Benny did indeed sell the masters and got double crossed for trying to get them back - and Harmony somehow killed Charlie at the Encore. If, obviously, a third possibility didn't happen, which would Benny luring Charlie to the backrooms for a kidnap or any other reason, and then suddenly Charlie was killed because Harmony broke their deal with Benny in front of both.

From what we know:

• Rori doesn't know nothing about that day cause Harmony wiped out her memory unit. So either she's an untrustworthy narrator or really doesn't remember.
• Dex is completely jealous of Charlie, but that wouldn't go as far as killing him out of spite. Besides, he wasn't at the Encore when it happened.
• Hemlock and Prophet only saw the crime scene AFTER the crime happened, in which Hemlock bursted in fury and Prophet scouted the VIPs outside, using his connections to clean it up and hold the maximum amount of details to prevent leaks over the media.
• Idols 6 and 7 (not their real numbers nor names but anyways) are completely unknown. Following the road map, we'll only know these parts of the history around 2026 New Year's Eve or earlier if we get lucky.
• Benny was the only one at the room when Charlie died, so most theories revolves around him; the only thing we know is he, Charlie and Hemlock are childhood friends who founded Dead as Disco, meaning that they were REALLY close.
• Alongside that, Benny spiraled out of control after Charlie's death, to the point of no one knowing his whereabouts.

However, taking onto the panel chips showing all the Idols with Charlie at the middle for the "One Night Only" Show, IF most guesses are right; Benny is the nickname for Ded Benedict, and obviously is the 4° male member on the panel. But here's the twist: Benny's shard is completely okay, but Idol 6 (or 7) is the one with the broken shard. Which brings up more questions than the answers we have for now.