No... an attacker that is able to successfully execute a 51% attack can crash the token price and make enormous profits in the derivatives market, so the market

No... an attacker that is able to successfully execute a 51% attack can crash the token price and make enormous profits in the derivatives market, so the market cap is irrelevant. Moreover, and attacker may have motivations other than financial gains, which again makes market cap irrelevant. If your security model only protects against financially motivated attackers it means it's basically rubbish.