I'm not so sure about that. Being CEO of a startup is not as glamorous as it is in the west, but money is available here for startups. After I finished my contract teaching English in Japan, I was torn between going back to programming or opening a brewery. Money would have been
no problem on the brewery side. Even just casually exploring the situation, I had more interest than I knew what to do with. I was even offered a
building to house my brewery.
As some other people have mentioned, I suspect SoftBank has a specific goal in mind and is buying up companies that give them particular capabilities. They're not just investing with the goal of getting a return. What their ultimate goal is, I'm not really sure, though.