SoftBank left millions on the table to engineer a win for Masayoshi Son

SoftBank Group Corp.’s Masayoshi Son, whose record on tech investing took a drubbing after flameouts like WeWork and DoorDash Inc. fueled a record $32 billion loss at its Vision Fund arm in the last fiscal year, was determined to turn the tide.

So as he and the investment firm’s other top executives met with bankers to plot this week’s initial public offering for Arm Holdings Plc, the focus was making sure the sale would go off without a hitch. They didn’t want any last-minute hiccups with buyers pulling out, they dreaded pushback on the valuation, and, most of all, they wanted to set a price that would almost guarantee the shares would pop on their first day of trading.