A result of the zombification of the japanese economy. The BOJ is buying stocks on all of these zombie companies to keep them alive and this is what you get.
It smacks of exactly the result you expect when the money they are investing isn't "real". When what you're spending is actually funny money, why not ring up a $1B+ valuation just for the sake of being able to call the company a unicorn? Maybe they are hoping for self-fulfilling prophecy. But underneath you have money chasing problems which are completely uninteresting, non-technical, or niche markets which will never support the valuation.
The money then proceeds to corrupt the teams which have raised it, because if someone just handed you half a billion dollars you better "put it to work" one way for another, even if the opportunities you are chasing don't measure up. The CEO convinces themselves their time is worth $50,000 an hour and suddenly it's irresponsible not to fly private, etc.
The money stops being real, becomes funny money, and the investment behavior changes.
In Japan, the problem is particularly absurd -- with the BoJ owning like 77.5% of their ETF market, and days passing where not a single Japanese bond sells (of which there are USD $10 Trillion outstanding, and the BoJ owns 43%!)