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.
Could you explain in a little more detail? Why wouldn't the Russians have any motivation? Didn't Skripal betray Russia? What would make Germans want to kill him? The article I shared implies that they've identified several Russians that were involved in the assassination attempt. You don't believe that? What makes you think that Russian assassins are better than Germans?
A simple cost-benefit analysis would show that clearly, a blatent poisoning like this has much more damage back home than it does good. Putin isn't stupid, if he really wanted revenge then he would do it in a way that wouldn't point all the evidence back to him. Russians are certainly not clumsy when it comes to spy work.
So who did it then? Well the "evidence" that the poison came from Siberia is far from damning--anyone can waltz across the border to Kazakhstan and then hop on the next flight to London with a bit in his pocket. But it certainly is a good way to lay the blame on someone...