Xcel
Look, I don't know how many times I am going to have to say this before you get it.
I don't have a theory. I don't have a model. I have nothing whatsoever to say about the character, training, skill, or professionalism of the pilot. Not even the somewhat abusive character that trained him.
All I have is a question. That's it. It's very simple: why would you leave a perfectly good, very long, superbly equipped runway to head off for another, some 20-odd miles away, with a major failure?
There is possibly a second question, which would be, why, when a second problem became apparent, or it became clear that there was going to be a problem reaching Bankstown, was a decision to make a forced landing not made while there was sufficient height to get it done successfully?
And that's all I'm asking.
Now to answer your points:
It has been verified that there was low cloud and fog in the area
By who? Everyone who has commented on the weather at Richmond has said there were no issues (posts 122, 130, 173 and 181). I don't know who is right and who is wrong, but I do know that I tend to prefer human observation to automated weather reports. It is perfectly possible for an automated station to report low vis at the surface that would in no way preclude a safe landing.
Then better we wait for a report. The contents of which I'm sure will interest many...
The report will tell you precisely nothing about the real causes of this accident - they are lost forever.