They use those things when they want the world to know it was them. The number of countries with access to Polonium or Novichok is extremely limited, and both are very easy and obvious to detect in an autopsy.
When they don’t want the world to know, they make it look like a suicide or accident, e.g. falling out of windows.
I don’t know what percentage of a population of oligarchs fall out of windows each year unaided, but when it’s the fifteenth or sixteenth it does start to get somewhat obvious that something untoward is happening.
They use those things when they want the world to know it was them. The number of countries with access to Polonium or Novichok is extremely limited, and both are very easy and obvious to detect in an autopsy.
When they don’t want the world to know, they make it look like a suicide or accident, e.g. falling out of windows.
I don’t know what percentage of a population of oligarchs fall out of windows each year unaided, but when it’s the fifteenth or sixteenth it does start to get somewhat obvious that something untoward is happening.