It is well known that Satoshi mined the earliest bitcoins, and that they sit untouched to this day, growing in value
Is this well known?
to attack that account first as the biggest, most well known large account
From what I know the early "satoshi mined blocks" are individually mined into their own addresses. So the holding is spread out among many different addresses, meaning there is no one "big account". There are much
bigger addresses that an attacker would target.
...threw away the private key
I doubt he threw away his private keys.