Well, let's make assumptions and look at facts
A1. (Assumption 1) Russians in FSB, GRU, other secret services are not complete idiots but rather smart guys. I describe the statement as an assumption while it is rather a fact.
F1. The chemists Ranajit Ghosh and J.F. Newman discovered the V-series nerve agents at the British firm
ICI in 1952. VX nerve agent and its properties were scrutinized later in Porton Down.
A2. The Russians are able to produce VX in their laboratories.
A3. HMG and mrs.May don't lie and indeed Novichok nerve agent was used
A4. Russian political leadership ordered to kill mr.Skripal in a demonstrative way, to poison him.
Now, let's suppose that all our assumptions are correct. But there is a contradiction. In this case evil Russians would use VX that directly points to Porton Down.
So at least one of our assumptions is wrong. What one exactly?
A1? Do you really think so?
A2? Do you doubt it is impossible to produce VX in Russian secret laboratories?
A3? Why not? It is quite possible. But those who blindly believe anything sounded by HMG have to recognize that only assumption
A4 is wrong.
So making assumptions and analysing known facts (also not mentioned by me directly) we come to a conclusion that Russian political leadership did not order to kill mr.Skripal.
Okay, I'll play. Let's make a couple of assumptions (A) and some Facts (F):
F1. Russia is having an election today. (Obvious)
F2. The new Czar wants to be the longest serving leader since Stalin (Obvious, he's on the ballot)
F3. Putin wants a 70% turnout and 70% of those to vote for him (according to Russian state tv)
F4. Russia under the new Czar wants to regain its 'superpower' rather than a 'regional power' status (based on Putin's speeches and actions)
F5. Putin's govt is run by crooks and thieves (according to you). It's basically a mafia state.
F6. Any opposition is ruthlessly suppressed be it Nemtsov or Navalny.
F7. The Soviets invented Novichok.
F8. The 'Russia strong' message is peddled by the trolls and 'useful idiots'
F9. The West is seen as decadent.
F10. The UK is the home to many Oligarchs and to former Russians who fled Vlad.
F11. Putin has threatened to dispose of the 'traitors'
F12. Russia has massive agitprop campaigns. There are many 'useful idiots'.
F13. Russia has used numerous vetoes at the UNSC to support Assad and his use of CW (and now Iran).
F14. Four years ago, Crimea was invaded and annexed.
A1. It's all about the US (according to agitprop and your posts)
A2. The UK is the 'chief poodle' or 'client state' as Russia see's it. (obvious, emphasised by you)
A3. The UK remains a thorn in Russia's side. Not so much on conventional military might, but the SIA (particularly GCHQ) and of course it has nukes as well. Plus one of the P5.
A4. Russian meddling according to the US Int agencies in their elections, so doing anything in the US for now is verboten. (ongoing investigation)
A5. Vlad wants to send a message to get more of a turnout at the election.
A6. Vlad wants to be seen as the only person who can 'save' Russia from their (the West's) meddling (freedoms) and their views (freedom of expression, gay rights etc.)
A7. 'Colour Revolutions' frighten the pants off Putin. (having seen the collapse of the CCCP)
A8. Russia wants to send a message (emphasise) to their populace, that the West is out to get them.
A9. Instead of the US, the 'chief poodle' will do for any 'lesson' to be made..
A10. Vlad wants less people prepared to betray the Russia he wants to be in charge of.
A11. If a lesson is to be made, it needs to be pinned down to Russia but can be conveniently denied, obfuscated and 'whataboutery'ed' (nod and a wink, but denied)
A12. Russia doesn't care about collateral damage be it Russian citizens or bystanders (Ukraine and Syria)
All of the above neither contradict anything nor any of the assumptions, let alone the facts. Possibly A8 & 9 assumptions can be queried. Bearing in mind facts 1 to 5 and 8 to 10, it's still a strong possibility. A11, high probability.
Anything to add?