All the evidence points to it being the Russians, Putin himself said it might have been "patriotically minded" Russians, all US intel agencies say it was the Russians, all non-US agencies say it was the Russians.

And you claim to be baffled as to why people say it was the Russians?

Maybe it wasn't, but it's not exactly baffling why people say it is. There are no real counter theories at all - the only counter claims sort of say "Deep State" but nothing else.

Where is the direct, observable, undeniable evidence?

If you don't have it, then don't keep parroting the nonsense.

b) What kind of evidence wouldn't you deny?