Masayoshi Son Is Going Big on OpenAI. Time to Worry: Shuli Ren

When Masayoshi Son bets big, it either marks the dawn of an era, or the dusk of a tech cycle.

The chairman of SoftBank Group Corp. has enjoyed some spectacular wins. Spotting Alibaba Group Holding Ltd. early handed SoftBank $58 billion when the Chinese e-commerce firm went public a decade ago. A $32 billion take-private deal of ARM Holdings Plc in 2016, followed by a timely listing of the chip designer in 2023 when the AI theme took off, gave Son another windfall. ARM now accounts for roughly half of SoftBank’s portfolio value.

But there were equally breathtaking failures. WeWork Cos.’s very ...