I am sorry for your loss Gemini
Perhaps I am wrong, but I do not believe that the T's abdomen size would cause it any problems during the moulting process.
In nature T's sometimes have an abundance of food and also grow large, extended abdonmens. There they mostly manage to moult and continue their existence without problems.
I have a rather fat Chaco Golden Knee (Grammastola pulchripes) around 5-7cm and the T seems to moult without issues, even though I sometimes wonder if I should reduce it's food intake.
More than likely, the humidity in the enclosure was too low, causing the T to tire during it's moult and pass away due to exhaustion.
Just my two cents worth. I may be corrected by some of the senior members, if I am wrong, I do apologise beforehand