It wasn't "written off", it was hushed up. It wasn't "as soon as it might be Russian disinformation", it was as soon as it was obvious how damaging it could be

It wasn't "written off", it was hushed up. It wasn't "as soon as it might be Russian disinformation", it was as soon as it was obvious how damaging it could be to the political objectives of those who pretend "report the news" if people were aware of this news. If it's not obvious on its own (de)merits, imagine if it had been information that potentially damaging to Trump. Would it have been "written off" at the first suggestion that it might be disinformation or shouted from the rooftops 24/7 every day until the election? That's the difference between reporting it or not based on "disinformation" or not vs. reporting it or not based on whether it would help or hurt the candidate you are campaigning for.