Satoshi really downplayed 51% attacks in his/her original whitepaper[1]:
> The incentive may help encourage nodes to stay honest. If a greedy attacker is able to
assemble more CPU power than all the honest nodes, he would have to choose between using it
to defraud people by stealing back his payments, or using it to generate new coins. He ought to
find it more profitable to play by the rules, such rules that favour him with more new coins than
everyone else combined, than to undermine the system and the validity of his own wealth.
Apparently he didn't realize that coins could quickly be transferred to other crypto and not held, so who cares about the value of the stolen goods.
> The incentive may help encourage nodes to stay honest. If a greedy attacker is able to assemble more CPU power than all the honest nodes, he would have to choose between using it to defraud people by stealing back his payments, or using it to generate new coins. He ought to find it more profitable to play by the rules, such rules that favour him with more new coins than everyone else combined, than to undermine the system and the validity of his own wealth.
Apparently he didn't realize that coins could quickly be transferred to other crypto and not held, so who cares about the value of the stolen goods.
[1] https://bitcoin.org/bitcoin.pdf