The article doesn't say so and I haven't found an explanation. Why was the audio only feed 8 seconds faster then the video feed? Why is this time difference needed?
Because it was a backup feed that was not supposed to be accessed by anyone unless the video feed failed, so it shouldn't matter if it is delayed or not.
Incompetence on the part of BoE and/or malice on the part of the third-party provider.
It's a truism that non-tech industries are really, really REALLY bad at basic technical things (like operating servers): banks in particular apparently had their Web security divisions run by 12 year olds well into the 00s. It's not clear to me what organizational or incentive barriers there are to competent tech outside of the tech industry, but I've grown to expect them