No they THOUGHT he would probably be found not guilty. They don't know that.
It's probably all money based. As in, the government don't want to invest the time, money and resources for what they think will be a waste of time. Or, that department doesn't.
But, that should be criminal in itself, the chick wanted to press charges... she should be able to. The DDP should be accountable to some outside party, or 2nd opinion on whether 'there's enough evidence', It seems perhaps the system in Ireland, especially regarding sexual assault type shit is... unless there's a fkn video of the assault happening... there's 'not enough evidence'. All you should need is probable cause, likelyhood, a credible and willing witness... and you had all that;
You have a battered, bruised woman with a tampon jammed up her fkn vagina, who went straight to a rape treatment unit, crying and in shambles, wanting to press criminal charges. Who had just been with a man (provably), right before what clearly appears to be a physical, sexual assault - who has been accused by multiple other women - and has his DNA in you. I'd say that's a pretty good fucking case. If not, wtf else do you need? Like I say, other than a video of the fkn assault happening.