My take is the branding, and only the branding, caused Keith Raniere’s downfall.
If not for the branding, DOS would have continued on just fine, likely even to this day. The result would have been a sizable library of sexual images and video for Keith to enjoy (when not taking advantage of the harem). The longer it went on, the less likely anyone would have come forward because the greater the threat that library would have created, even for those not in DOS.
The collateral system was clearly inspired by Scientology’s Auditing. While that cult added a bunch of nonsense to it, it is really just getting Scientologists to confess anything negative they have done or felt at any point in their lives. The Auditors would record and thoroughly document these sessions. The result is substantial blackmail material that can be used to at least ensure silence. Which works. Most ex-members refuse to talk about the cult for this reason. Not just to protect themselves but also protect friends and family that remain in or left the cult that could have their material released.
Eventually its possible DOS would have internally fallen apart once Raniere’s part in it came out, but its likely that collateral would have prevented it from becoming public. Lets be honest, the NXIVM-5 do have one thing right – the only reason Raniere got investigated at all was the public notoriety of a harem inside his cult, a harem discovered via the branding.
Without that attention, there would have been no investigation and thus no knowledge of any of the other crimes he committed. At most rumors might have made their way to local police departments, who once saw Raniere was backed by two heiresses and their lawyers would have immediately thought “these people volunteered for this shit, we got bigger problems to deal with” and never made its way to the federal level for investigation.
In short the branding, not DOS and the collateral, was the bridge too far that led to his downfall.