so
A) Satoshi has other earnings, in bitcoin, that was held long enough to make Satoshi extremely rich, and sold under their normal known identity. While never needing to associate with the other identity.
B) The private keys to the bitcoin mined in those original blocks were sold for cash over the counter for very large amounts to funds with longer time horizons. Bitcoin can operate in temporarily trusted environments. Bitcoin price has tanked every time very old Bitcoin is transferred onchain, so there is no need to transfer them onchain. We would never know.