Could you please show your work? We all know what they say about assumptions. But I'd say in this case, it's equally likely that the manner of death was carefully chosen to send a message to those still living. To wit, "You will never be safe, no matter where you go or what you do. There's no end to the ways I can kill you, and I don't give a **** about appearances."
This is the Internet, it's all guesses. I'm sure the intent was to cause fear. But previous posts above listed very close up and personal methods of elimination. That's a message not just that a person can be removed, but that you have no protection for someone just walking up to you and doing that. That's not a Putin thing, that's a Russian thing.
If this episode was either sabotage or AA, to me it sends a message that for the first time in 100 years a relatively independent political figure can protect himself on the ground from the national leader. If they hadn't brought down the plane, it could have been stated or assumed that they didn't want to. By this act, my math, this demonstrates that it was the only option they had, the best they could do.
Or in other words, to me, what was meant as a threat was really an indication that he has such little control over his own forces that he effectively has to use terrorist tactics within his own country in order to eliminate a single person. As others have pointed out, that's the act of a drug cartel leader, not a head of state. Perhaps more accurately, an act where your options are limited because your reach and control is limited.
Maybe I'm all wet on all of this. But I see taking down an airplane as a Pablo Escobar thing, which didn't work out exceptionally well for him, leading to a reach out and touch moment that Pablo was on the receiving side of. The latter of which absolutely was sending a message, at least in my view. And extending that, maybe my weird math means that the Russian fellow may have been more vulnerable to Prigozhin than Prigozhin thought...and maybe still is vulnerable to internal opposition.