> They had hundreds quiet of ways to kill Sergey
Sure they did but that clearly wasn't the goal or, at least, not the only goal. Anyone who thinks that this was somehow an incompetent operation doesn't know what they're talking about. The GRU are just doing what Mossad has been doing for years. And they appear to be doing a pretty good job of it.
> how did they know that it was specific to Russia?
Not specific to Russia, specific to a lab in Russia. As they can't publish the actual analysis, I'm going to make an educated guess that they look at trace elements in the poison. Every lab will have a signature. I have no idea whether it was from the poison itself, the solvent or something else. What was clear though is that the UK lab couldn't trace it but the Swiss could.
> convert it to evil in eyes of all
Nah. This is small potatoes compared to the invasion of Crimea.