I'll throw out a little more speculation: Get-there-itis is the term for the cause of most of the bad decisions in aviation.
I haven't really dug into the details, but I was under the impression that the helicopter was holding just outside of a Class airspace for 10-15 minutes waiting on the Special VFR clearance. Looking at the limited data from one of the early articles, I couldn't quite wrap my head around why a helicopter would be scud running that close to terrain at those high high speeds. It's a poor decision.
If there was pressure to get somewhere at a certain time, which caused a decision to fly in questionable weather, and the questionable weather caused a delay due to waiting on an SVFR clearance, and that delay resulted in a decision to run a little fast... it's that classic case of compounding bad decisions.
The other question is why they didn't just file IFR. The only things I can think of is:
1. They wanted to sightsee
2. They were landing somewhere that didn't have an approach (i.e. not an airport)
3. The pilot wasn't IFR current... but that seems unlikely as I can't see the insurance companies not having that as a stipulation.