There really isn't a debate in that. They reported it didn't exist, it did. They reported it was Russian disinformation, it wasn't. This happened on a large scale.
So your claim is that it was large scale incompetence, rather than dishonesty. And that Fox News was the only outlets that wasn't incompetent?
I think you are discounting bias in a way that you wouldn't, and shouldn't, if it came from Fox News.
This was an aggregious failure. I'm not confident that it is the last time it will happen either. You are?