A smart attacker would create his pool ahead of time - e.g. one of the current pools could actually be the attacker. They would have two versions of the mining pool SW - version #1 is the "honest" one, they would run this for a while, likely with low-to-no fees, to get a reasonable user base and reputation. Then, when they feel they are ready, they would DDOS enough other pools to make people flock to theirs. Once they hit 50%, they would activate version #2 of their mining pool SW, the one that steals coins/double spends/whatever. Since they own more than half the hashing power at that point, they win. People will eventually figure it out, but when they do, confidence in BTC will be crushed and you would see a crash in values.
You miss the quote from Satoshi's paper:
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.
Of course there are sociopaths, who don't want make money. But usually they can't raise capital. And the notion of state (who doesn't need to be for profit and have capital) running >50% of network power to double spend seems to be absurd to me (though i can be wrong).