(Bloomberg Opinion) -- As Japan's SoftBank Group Corp. unloads about 200 million shares of T-Mobile US Inc., more investors get a chance to own a top-performing stock that had been hogged by insiders. SoftBank's fire sale isn't a knock on T-Mobile, but rather a reluctant move by billionaire Masayoshi Son to shore up his own troubled conglomerate. Indeed, his loss will be someone else's gain.