What the point of keeping all of it of you can never spend it?

With such whale, even if it sells and crash the market by 80%, it's still a massive profit and can be reinvest in other assets and back to BTC at lower price and over a long bear market.

But I also think it will not be sold but officially moved to the tresury of a newly created company or something.

And if Satoshi is behind it, for what we know he could have kept a few thousands to live an easy life under the radar, just to suddendly come back in 1 or 2 decade, once Bitcoin is adopted enough and too later to roll back to fiat and instantly claim himself leader of the new Bitcoin world.