The most logical explanation is that the event was ordered by the " Deep State", and the hit was done by a German EU asset working in Porton Down. Had the Russians done it, then it would have been a professional hit, not the amateur botch up that one expects from EU "assets". There is no conceivable reason for the Russians to have done it, by the way.

That is the only explanation that fits all of the "facts" that have come to light.