The radioactive plume was detected in foreign countries, which is hard for the Russians to stifle!
Our press and government (close to the same thing, CIA has a HUGE role in the press) would have passed 9/11 off as an unfortunate accident if only one plane hit the WTC, and as a bizarre coincidence if there has been one in NYC and Flight 93. The only reason it was reported as terror is that so many planes were involved.
The Soviets had no intention of telling their own people even if the West knew about it. Back then, the internet was in its infancy and no Soviets had access to it.
As for 9/11, the use of four planes was deliberate to make sure every American knew it was terrorism on our shores. And every American was angry and filled with resolve against the people who hated America and attacked us, so much so that...
...just seven years later they put one of them into the White House. All thanks to s complicit democrat/communist media/entertainment/academia propaganda complex.