Putin has transparently murdered dozens of people far more important to the West without being toppled.
Russia’s newly displayed military impotence shifts the calculus, but Prighozin isn’t the guy to cause an international uproar.
That isn’t however the argument the article is making (noting I’m rather dubious on it).
They’re not arguing that NATO will suddenly invade because Pringles got SAM’d.
They’re arguing that a) the Wagner lieutenants are competent and experienced which makes it likely that they are not only capable but likely to be effective at seeking vengeance; and b) that Putin has systematically culled all the competent generals and hence there’s a reduced capability.
Now I’m dubious on the likelihood of the first, and while the second is true I’m not as convinced it will be a game changer.