That’s true in average cases but at the highest levels of power, having inconvenient people killed is just another power like getting caviar delivered by private jet.
Yes, but we can also use Bayesian methods. If someone with powerful, murderous enemies dies in an extremely improbable way, it's not statistically sound to just say "accidents happen every day".
Of course you would need proof to actually convict someone, but it could definitely be a legitimate reason to start asking questions.
"Motive, means and opportunity" is typically what investigators need before charging someone with a crime so not quite sure if it follows that it's not supposed to be brought up in court?
If you include legitimate killings by military personnel, there's a LOT of killers walking the streets. It's a very standard part of life that's hard for most people to really grasp.
Once you consider that there are literally thousands upon thousands of legitimate, legal killers in the country, and a smaller set of people with the power to order those killers to do killing, it really doesn't make sense to assume that all the killing is above board.