They are absolutely not basing everything on those two things you mentioned. I don't think there is anyway, a couple of assholes on an internet pot forum, would be privy to everything they are basing their investigation on, but if you want to look at it anecdotally, it's easy enough.
1. They've done this many times before.
The long, terrifying history of Russian dissidents being poisoned abroad
https://www.washingtonpost.com/news/worldviews/wp/2018/03/06/the-long-terrifying-history-of-russian-dissidents-being-poisoned-abroad/?utm_term=.e9b5d6b64b99
The long history of Russian deaths in the UK under mysterious circumstances
https://www.independent.co.uk/news/uk/home-news/russian-deaths-uk-history-spies-murder-sergei-skripal-alexander-litvinenko-a8242061.html
to people like this guy:
2. The OPCW report
https://www.opcw.org/fileadmin/OPCW/S_series/2018/en/s-1612-2018_e_.pdf
The results of analysis of biomedical samples conducted by OPCW designated laboratories demonstrate the exposure of the three hospitalised individuals to this toxic chemical.
The results of analysis of the environmental samples conducted by OPCW designated laboratories demonstrate the presence of this toxic chemical in the samples.
The results of analysis by the OPCW designated laboratories of environmental and biomedical samples collected by the OPCW team confirm the findings of the United Kingdom relating to the identity of the toxic chemical that was used in Salisbury and severely injured three people.
The TAV team notes that the toxic chemical was of high purity. The latter is concluded from the almost complete absence of impurities.
The name and structure of the identified toxic chemical are contained in the full classified report of the Secretariat, available to States Parties.
That's 2 things they could be basing this on, is that enough?
As to all the you guys stuff, I'm only speaking for myself, but no, I don't believe everything my government tells me. No my butt doesn't get all hurt, when people choose to believe Russia Today because I, like most people, know that it's the propaganda arm of the Russian government. I actually smoke really good hash and go on a pot forum and mock those people.
As to your last part about wmd's and Iraq and they are the same people pushing for war again, your saying Colin Powell poisoned those two Russians? Because he was the wmd in Iraq guy right?
Or are you saying Bush poisoned them? You may be unaware but his momma just died so he's probably pretty busy with that.
Do you have a source that says otherwise , that isn't funded by the Russian government? I'd be happy to look.