Earlier quoted context omitted.
The attempted murder of Sergei Skripal by Russia is a conspiracy theory? Who else would poison him with a nerve agent? Who else would have the motive? Who'd have access to such an agent?
All of the evidence that it was Russia is entirely circumstantial, if we're being strictly accurate here, which is... convenient. On the other hand, exactly zero other groups seem to be using those nerve agents to assassinate people, so it's a great calling card if they wish to discourage others from following in the victims' footsteps.
I don't know what other conclusion to draw.