Jesus fucking christ. They haven't. All of mainstream media has been covering it since it happened.
New York Times: https://www.nytimes.com/2023/02/04/us/train-derailment-fire-...
Washington Post: https://www.washingtonpost.com/nation/2023/02/04/east-palest...
CNN: https://www.cnn.com/2023/02/04/us/east-palestine-ohio-train-...
AP News: https://apnews.com/article/pennsylvania-ohio-evacuations-fir...
NPR: https://www.npr.org/2023/02/06/1154760911/ohio-train-derailm...
Reuters: https://www.reuters.com/world/us/ohio-carry-out-controlled-r...
The Guardian: https://www.theguardian.com/world/2023/feb/04/blaze-from-50-...
CBS News: https://www.cbsnews.com/news/ohio-train-derailment-causes-bi...
ABC News: https://abcnews.go.com/US/train-derails-flames-ohio-causes-h...
USA Today: https://www.usatoday.com/story/news/nation/2023/02/05/ohio-t...
CNBC: https://www.cnbc.com/2023/02/06/-controlled-chemical-release...
A simple Google search can show many, many other examples.
>Was the thought process that something like this, which is killing frogs and small animals at a rapid pace, could be easily covered up?
It wasn't covered up by anyone, anywhere, at any time, at all.
> What are these stupid "China balloon" and UFO distractions?
They aren't "distractions," they are other newsworthy events occurring simultaneously and in parallel to the train derailment story. The media didn't stop covering the train derailment in order to focus on the balloon story, rather it covered both, along with other stories unrelated to either, because the media is capable of covering more than one event at a time.
People are also capable of being aware of more than one event at a time. People who were following the balloon story were also aware of, and concerned about, the train derailment.
It just happens that the balloon story became more viral because it got wrapped up in the whole UAP/UFO thing. But that isn't a conspiracy by the media to distract from "the real story," either. It just happens to be more fun to talk about UFOs and Chinese espionage than an environmental disaster.
> Since Twitter is at least a degree less censored now, is this only just being covered now because news has leaked out to the "general populace"?
The general populace has been aware of the train derailment since it began, and the mainstream media has been covering it since it began. The story has not been censored, either by mainstream media or social media.