I mean the Johnson story has not been buried. You have proven this by linking to the story published on the news website of our major natoonal broadcaster.
It was also the lead story on BBC Today and Breakfast programmes yesterday.
You will also notice the Johnson story came from revelations in a documentary the BBC is currently running on prime time BBC2.
What is driving the Brand story is people like a scandals, especially ones about sex. The media cover stories that drive clicks/sells papers. The media also loves stories about themselves (a major component of the Brand story is allegations that his employers turned a blind eye and sometime even enabled his behaviour).
Yes stories can sometimes be released on days when media will be looking tbe other way (embarrassing reports etc..) but this is not what happened here. This was the BBC running a story to promote their own TV show that was airing the next day.
When people say stories have been buried or not covered what they often mean is their media consumption is narrow or they are woefully media illiterate.