It's much more likely that they just pinned this story on some guy who died in a motorcycling accident.
The point of killing someone over some wrong they did you is publicizing it after the fact. If you don't take credit for it, it doesn't have any deterrent power.
Or alternately, they staged what appeared to be a fatal accident to put him in a witness protection program.
Or alternately, he did it and then tried to back out of the deal. Now arranging an apparently accidental death then became the best way to keep security intact.
The one theory that makes no sense is that they intended his death from the beginning.
All believable scenarios. I personally am fond of the "pin it on a dead guy" story. I want to believe that western security services have some sense of elegance.
The problem with killing an asset is that you've now involved multiple more teams of assets who now know that you kill assets. This is not how you keep secrets, nor how you retain people who keep secrets.
Like the JFK assassination theories that involve killing off an additional dozens of people. You can't cover up one murder by involving an extra 1000 people.
> If you don't take credit for it, it doesn't have any deterrent power.
The various deaths associated with Putin are a counter example here. Russia denies involvement but the method usually makes it pretty obvious. Rare poison, unlikely situation etc.
The putin assassinations are a little different though. The assassinated are publicly known to have links to the regime. The methods of death have a similar signature and the rarity of that type of death makes most people draw one likely conclusion so that the message is communicated. People fall out of windows for minor infractions and to really send a message they are poisoned.
The asset in this case wasn't known publicly and the method of death makes people assume it was simply an accident. Unless they did some private announcement, no one was deterred. If it was Iran and they wanted to send a message, they would probably have to out the asset publicly and/or make it clear that it was an assassination. e.g. a bomb would send a clear signal that it was more likely to be a nation state assassination and not some accident or a random robbery/act of violence.
The point of killing someone over some wrong they did you is publicizing it after the fact. If you don't take credit for it, it doesn't have any deterrent power.