Hersh thinks, as of Feb 23 2023, that "the Russians have yet to put any of their main forces in". (https://twitter.com/JimmySecUK/status/1628898816953909251) I dunno what happened to him, but you should probably read his allegations with that context in mind.
Purely speculative conspiracy theory here.
Yes, that's why US does everything they can to prevent investigating who caused it, same with UN and US allies when it come to investigation who sabtaged NS.
But of course it's conspiracy theory, let's just label it and ignore smoking gun.
The other possibility is EU member states and investigating it would further inflame internal tensions in an already tense time and erode support for the war effort. There are many many possibilities - which is why the version you are putting forward is labelled a conspiracy theory until otherwise proven.