Probable cause can be based on nothing more than someone's statements and is open to conjecture. DAs only move forward, typically, on cases they think they can win. The Michael Jackson case is an excellent example. I believe brother Michael was gulity, but having seen the pathetic opportunist 'victim' and his family, the jury favored MJ. I think they beleived MJ was guilty as well, but the prosecution's witnesses were awful. Woody's case is so much more shallow, based on what I know (and I admittedly am not an expert but I doubt anyone else on this site is either ). If they thought they could have won the case they would have moved forward. An expert panel didn't think he did it.
I have empathy for Dylan. I don't know the truth. But, if what Woody Alllen said in his response is true, his credibility is higher. An expert panel beleived that a long time ago. He may be lying. I do not know. He may be a molester. I do not know. But Soon Yi and the girl on Piers Morgan, although raising some suspicion, are not 'proof' about anything. As I understand, both Soon Yi and the woman on Piers Morgan say very good things about Mr. Allen. But I know that those certified to administer lie detection analyses are held to a very high standard. If my memory serves me correctly (don't hold me to this because it has been a long time and I didn't spend the time reseraching), O.J.s lawyers also hired ther own polygrapher and O.J. failed.