It was hardly his life's work as he was only there 11 or so years. He went on and did other things, remember? And he created the circumstances that led to the hostile takeover.
But it's a simple fact that other TSR employees and contractors - such as Tom Moldvay and J Eric Holmes - were better writers, and better-organised writers, and they were much better at collaborating with editors.
You mixed up fact and opinion again,need to work on that. Also you might want to look at the time tables on those people you mentioned and what happened to them.
Gary Gygax was in my opinion a brilliant game designer who risked a lot on what he saw as the real possibility of what this new hobby he created(with the help of others) could do and then he did what no others were willing to do, he sunk everything he had into it. All his money,all his time and effort and risked it all for what he believed in.
He did have some business sense but for sure that side of his skill set was not all it needed to be. Over time his character flaws and the character flaws of those he worked with lead to some pretty sad ends for our hobby.
Still,because of their work and risk we all have a great and growing hobby today and millions of lives were positively impacted and our world is a slightly better place to live.
Some of us knew Gary even if it was mostly on the message boards or email or the rare con we might make it to. We loved Gary and miss him. He was our friend.
He wasn't just a name in the history books. So when we read someone say "It's a shame that Gary wasn't forced out earlier so that, perhaps, Tom Moldvay and a competent editor could have written AD&D. " It's difficult to not have a knee jerk reaction and bring out fire and torch.
The man was mortal and had flaws and things he could have been better at so,it is fine to point those out if it betters our hobby to do so. Just please keep in mind those things are not said in a vacuum and many of us still mourn his loss.