We spoke to 12 SoftBank insiders about how the $100 billion Vision Fund lost its way

SoftBank's Masayoshi Son has enjoyed a 40-year career in which he built SoftBank into one of the world's largest tech investors and became a billionaire in the process. 

But Son is facing one of the biggest challenges of his career, with the $100 billion Vision Fund racking up billions of dollars in losses, large investments...