i would imagine that by "impossible" they mean too much hard work.
they would need to track down the victims and persuade themt o give evedence again...37 years after the first cock up. and then try and get enough evedence to convict...which is difficult.
Sadly 6 months is pretty standard for jumping bail on the first occasion and as this is all he was sentanced for its about right.
I agree that he shold be held to account for his crimes against those boys, but sadly the CPS will look at it that the boys have moved on from what has happened and it would be too traumatoc for them to reopne the case...and that they have more recent offences to dealw ith.
Hopefully one of the victims will have seen this in the news and will get a private summons against him.