The Keiretsu based structure bred complacency & selling average products to each other.
As innovation technology in Silicon Valley skyrocketed, Toshiba made slideware & agreements that offered no tangible value.
They would talk about the cloud, sign agreements with IBM but have zero real budget for implementation.
Instead they would focus on continuing to build and sell non competitive solutions that meant divisions were ordered to keep making non competitive products built by thousands of engineers at a loss.
The board cooking the books sealed their fate.