I think it's worth pointing out that not just were there 20 women that the Guardian spoke to, but that the Guardian also corroborated the individual women's evidence by speaking to, amongst others: their partners, friends, parent, NC's manager that one of the women complained to... This is as rigorous approach as the police should take if investigating.
These are not just women "speaking out now" (my quotes about a sentiment I've seen on twitter and even here about why they're coming forward & speaking out now); these are women who complained/were upset/distressed/unsettled about the behaviour AT THE TIME, with some of that time being years ago.
Why didn't they speak up more? Well probably power imbalance, needing a wage and a reference, because they weren't sure if it was "enough", because they worried about whether it was worth potentially harming (a man's) career over. Earlier this week or last I was dismayed at the attitude shown by a couple of posters on the higher education board who between them said that a certain girl was happy that men were leering at her chest and that she was vacuous for doing this, and that women should think twice about "carelessly" saying things that could destroy a man's career.
When is a remark or action "bad enough" to officially complain about? It's a thought a lot of girls and women have.
As a PP remarked, Ashley Waters has put out a statement saying he is "shocked" at the allegations. The PP was naturally sceptical of how shocked he really was. My guess is that part of it was genuine shock for him, because the leering or inappropriate comments that he probably definitely witnessed just seemed like "banter" and "laddishness" and "flirting" and not bad. If he thought like that, and genuinely wasn't aware of the touching women sexually or filming them naked without their consent or pressuring them to take their clothes off and do sexual scenes or sexual favours... well then I can see that he may well be shocked. But that's the rub, many of us know that the more "inoffensive" comments and behaviour is often very much the thin edge of the wedge, and that the pervy attitude they demonstrate comes along with a sense of entitlement and power and a disregard for consent. However to many others, this 'thin edge of the wedge' behaviour is maybe inappropriate but ultimately inoffensive or harmless. So it doesn't get acted on or modified, and people don't check themselves because they know they're not participating in the more "serious" stuff.