TMZ Reports.. Kobe Bryant Killed In Crash!!! RIP KOBE! May god watch over your family! You and Gigi will always be loved!

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.
"Get-There-Itis" is the big 'no-no' for any pilot (and/or aircraft) that is not equipped to handle difficult weather conditions.
In my speculation, the flight originated in an area (John Wayne Airport near Santa Ana) that was not experiencing conditions as poor as what they were about to fly into. The flight to Glendale over Interstate 5 was very uneventful. But this Special VFR flight was asked to circle low over Glendale until controllers allowed the S-76 to proceed. Continuing northwest over I-5 allowed them to remain clear of the mountain ranges to the east and north before he would turn west and then southwest to intercept Hwy 101 that would take them all the way into Thousand Oaks where the Mamba Center (the place where the scheduled basketball tournament was being held) is located.

I believe your point #2 is the answer to the 'Why not just fly IFR' question. Kobe Bryant and his fellow passengers were likely being flown directly to the facility. There appears to be an area just across the street from the facility that was suitable for an S-76 approach and landing as long as the visibility was suitable. I can't say for certain, but that may have been their way of avoiding all the time-delaying traffic and they may have assumed that on the (approximately) 30 minute flight the conditions may not have been any worse at the destination than at the point of origin. They were wrong. It got much worse.