Because Russia has somewhat of an oil monopoly in Europe and the US doesn't like that. We've been being fed Russia war propaganda for at least a decade. If it even feels like a "Russia kind of thing" to the general public that is just the result of intentional conditioning by warmongers.
It could have been literally any major world power, including our allies. No evidence has been presented whatsoever as to who the culprit is.
Yes, one must see the most recent coverage to know the current story. ISTR someone had retired from CIA and was shopping a memoir around; apparently the only exploit he could mention on the record was that one time he got sick. Just his bad luck that in late 2020 we're mostly thinking about a different illness.
The only common element among USA facilities in Havana, Guangzhou, and Tashkent is the USA facilities themselves. Much like the situation described in TFA, those facilities were built by the most corrupt bidders. It will surprise no one when it is revealed that some corner was cut, and American personnel were exposed to harmful amounts of some ghastly chemicals, radiations, etc.
It is literally a conspiracy theory to reject this simplest possible explanation in favor of some outlandish three-way joint venture among the Cubans, the Chinese, and the Uzbeks, three nations not known for ever having done anything together.
Psychological conditioning is my theory. If you think about it, has this not been a rather popular news item for many years? If people should not get their perception of world affairs from the news, then from where should they get it?