Japans economy was much more government managed than completely free at that time. Specifically the Japans Ministry of International Trade and Industry ("MITI"

Japans economy was much more government managed than completely free at that time. Specifically the Japans Ministry of International Trade and Industry ("MITI") was steering the economy, mainly be using a control called "windows guidance". By given "window guidance" the commercial banks the Bank of Japan controlled which segment of economy was allowed to get what amount of credit. This turned out to be highly competitve compared to the western model of a completely free market economy. This system was later abandoned due to pressure of the US to make the banking system and the BoJ "independent". The result from this operation was that the commercial banks diverted more credit away from real investment to financial markets and assets investments, which in turn resulted in an unsustainable real estate boom in Japan. From of this real estate boom Japan never recovered when the bubble burst. BTW: The Bank of China uses nowadays window guidance as a system to steer the economy - and seems to be pretty successfull with it.