I didn't say professional pilots were immune to CFIT but the S92 certainly had mitigating factors and the 139 had severe operator/owner pressure, I'm not sure which 109 you refer to.
The 92 had errors in its navigational database and perhaps a crew that were too comfortable following the magenta line.
The 139 crew should have said no but pushed on using an inappropriate departure technique.
There have been far, far more GA pilots hitting the ground unintentionally over the years and the root cause is often poor weather appreciation and unnecessary risk-taking due to pressonitis.
I will defer to your experience and give it the respect it deserves but the common thread with all is that a human is behind the controls.
Someone suggested the human factors weren't covered so well and I would think the AAIB might recognise that hasn't been their strongest area as they recruited for that exact role recently.
All that said there is only so many times you can pass essentially the same message, in this case the pilot was experienced and one must surely be generous enough to think that a pilot with 3650hrs can read and understand TAF and METAR and F215 information. Why the obvious wasn't heeded is no clearer here than the fuel situation in Glasgow or the decision making of the 109 pilot who crashed in London or the two crew members of the 139 in Norfolk.
Pressure? I'm sure in most of those, I understand that this pilot was enroute to a wedding and for sure you can well imagine if that was the case it brought pressure.
If he was using an iPad as his primary nav did it freeze giving him a false impression of his position? who knows and one would still be pulled back to the preflight weather info and airmanship around continuation of a VFR flight into IMC.
But all that to one side people err and plenty of "great guys" have been caught out too and paid pilots are not immune.