> This article seems to suggest it's near impossible to leave a megacorp and start a company. So how did the first megacorps get started in the first place?
Japan's main modern megacorps largely are the same entities that were major business from the time of the Meiji Restoration (and some were founded much earlier, and are older than the US), or remixes of those entities that occurred when some of the old zaibatsu were broken up after WWII. They were formed as megacorps, for the most part, through very intense relations between government (both national and clan governments) and business industries, with a major component of that formation being either new or existing private enterprises whose founders had government connections taking over (often, at least initially, by leasing) the facilities of government business enterprises.
Those megacorps clearly aren't an indication of entrepreneurship in modern Japan. (That's not to say that such a thing doesn't exist, just that "how did the first megacorps get started" has nothing to say about it.)
Japan's main modern megacorps largely are the same entities that were major business from the time of the Meiji Restoration (and some were founded much earlier, and are older than the US), or remixes of those entities that occurred when some of the old zaibatsu were broken up after WWII. They were formed as megacorps, for the most part, through very intense relations between government (both national and clan governments) and business industries, with a major component of that formation being either new or existing private enterprises whose founders had government connections taking over (often, at least initially, by leasing) the facilities of government business enterprises.
Those megacorps clearly aren't an indication of entrepreneurship in modern Japan. (That's not to say that such a thing doesn't exist, just that "how did the first megacorps get started" has nothing to say about it.)