The report states he was in cloud when he hit the crane. Not a nice way for it to happen but we have all done stupid things and unless you have been trying to say VFR in inclement weather, you won't have an idea how easy it is to make this error.
I have yet to see a helicopter drop from the sky due icing and I have accrued a far bit at times. Freezing Fog is the worst but when you are in cloud, low level and you suspect it is clear on top - it pays to climb.