SoftBank’s Woes Are Mounting

Plunging profit, wobbly shares and a key executive’s departure after a bitter pay dispute beget the question: Will SoftBank rein in its freewheeling ways?

For the past decade, SoftBank and its founder, Masayoshi Son, grabbed headlines mainly for the Japanese conglomerate’s eye-popping investments, becoming a fixture in the American technology scene by spending freely on start-ups and fundamentally reshaping how such companies had been funded.

There was the world’s largest tech investment fund. The billions of dollars pumped into WeWork, the co-working giant. And Mr. Son’s splashy purchase of one of Silicon Valley’s priciest homes.

Now, the bad news is piling up.