The Bitcoin whitepaper states - "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."
I don't quite understand as to why? Can someone explain as to what can an attacker gain if he has more than 50% computing power and how it is outweighed by what he can gain if he plays by the rules.
The question What can an attacker with 51% of hash power do? does not seem to answer my question as it does not clearly seem to explain WHY is it more profitable to play by the rules.