Why do helicopters crash in low visibility (IMC)? There are no known direct eyewitnesses of the crash of helicopter flight Sikorsky S-76B N72EX with 9 people on board, including Kobe Bryant. However, there are many earwitnesses who heard the helicopter flying over their heads, but weren't able to see it due to extreme fog at the site, shortly before it crashed into a hill. Therefore, extremely low visibility was the probable cause of this helicopter crash. By assuming that, here's the question:

Why do helicopters crash in low visibility (instrument meteorological conditions IMC)?

For instance, what are current theories about the sequence of events of the helicopter crash of flight N72EX, assumed the crash happened due to the low visibility on site? Why did the pilot suddenly increase altitude above Ventura Freeway 101? And why didn't he follow freeway 101 by GPS (on this high altitude), although he was a certified IFR pilot flying under special VFR? And after his ascent, why the slow turn to the left followed by a sudden increase in speed while diving into the hill at about 4000 feet per minute? (Primary source: Flightradar24) (Note: ATC recording doesn't provide much useful information...)

[Note: I'm not interested in the many different theories or speculations about the crash of flight N72EX, just what are the most probable events that lead to the crash, if it was indeed caused by low visibility? Btw the crash flight N72EX was just used as an example. Actually, any other helicopter crashes caused by low visibility could be described in details as well, if they contribute to answering the main question. Please answer by using primary and secondary sources as well as some logic, physics/aerodynamics and psychology, thanks.]
The only flight rule that will completely eliminate human error is to ban people from flying planes or programming UAVs.

More regulations won't solve this.  Aviation is already strictly regulated.

As for why the pilot did not climb, well, you will have to ask him.

Keep in mind that a mechanical failure could be to blame.

We just don't know.

Answer to the previous question:
The risks of continued visual flight into poor conditions are already pretty well documented.  It is a serious hazard for all flying machines, not just helicopters.  We don't know if that is what caused the crash or is even a contributing factor, though some of the makings of a CFIT accident are present (bad weather, possible perceived pressure to go, and possible complacency due to familiarity with the area).  Anything we say here, including what I just typed, is pure speculation.

We don't know why the helicopter crashed and we will likely never know for sure.  It was not equipped wIth a CVR or FDR nor was it required to be so equipped.

This is a tragic accident and that's all we know.