FermatsTheorem can't help thinking that's because they got their reporting on it doubly wrong. Namely by both minimising it and then failing to accurately understand what went on once they did acknowledge it was sexual violence on a huge scale.
And it would have been such an opportunity to discuss, with nuance, a problem with many Western European immigration systems.
The perpetrators were from the Maghreb, who'd been in the country for years, had been denied permission to stay and should have been deported long before that NYE. But their home countries had denied Germany permission to fly these guys (and they were all guys) home. They were denied all recourse to public money and increasingly turned to crime, causing issues in many places (but Cologne was the largest by a huge margin). But the authorities just ignored the problem. Until Cologne.
This is another manifestation of the problem that resulted in the Rotheram scandal: when immigrants do actually cause problems and commit crimes and the authorities fail to deal with it for fear of being labelled racist by the left.
This was massively discussed on German TV debate shows once it became known that it wasn't Syrian refugees but almost exclusively long-term, failed asylum seekers known to the authorities.
But that's largely been unreported in Britain because the liberal media got egg on their faces decrying reports of the event as made up and racist, then had to admit it happened, and then they were hand-wringing so hard over how to frame the issue without demonising refugees while still blaming them that when the full facts became known they would have had to admit to getting it wrong twice. Beyond embarrassing. So I expect most reference to Cologne NYE to be exactly like that - in passing, without looking at the details.