A civil action requires the accuser to demonstrate that on the balance of probabilities they had been attacked or looked at the other way round the accused would only have to demonstrate that on the balance of probabilities they hadn't molested their accusers.  

There have been a number of cases where victims have sued their attackers despite them being found not guilty in court or never actually being charged with an offence - the Bill Cosby case being a prime example.

All this suggests to me that the CPS are getting it just about right.