It is a massive failure of policing. Sexual assaults occur in all countries but not on this scale. In such a public place.
TBH I think this is looking at it backwards. Objectively speaking, there aren't enough police in any Western country to force people to obey the law. Rather, the majority of people obey the law because they've been raised to do so and to believe that most laws are broadly correct. If enough people decide that a law is ridiculous and start to flout it, there is little that the police can do. Usually what happens in those situations is that eventually the law gets changed until it reflects majority public opinion again, or just disregarded as unenforceable by the authorities.
The authorities police by consent and are very aware of this. It's entirely back to front to say the police have failed because a sufficiently large group of people are refusing to consent to being policed.
What we are seeing is mass civil disobedience. A refusal to abide by, or consent to being policed on, Western laws around assault, sexual harassment and gender equality. If we don't ditch the mimsy apologetic 'all cultures are equal' business and come down hard in favour of our values, with the force of law, public opinion and the police, we might as well accept that women's equality was a flash in the pan and we're drifting steadily back to headscarves and being chained to the kitchen sink.