I would put a somewhat different interpretation on the matter. If Robin's leadership proved poor, they would turn on him in a moment. Why? Because they're Chaotic and have no loyalty beyond what has been earned.
Where does this idea come from that chaotics will gladly accept leadership as long as a sufficient sum of gold is placed in front of them first? I don't find 'mercenary' in any of my books as synonymous with chaotic, any more than I can find 'introvert' or 'unthinking'. Sure, a lawful individual's *perception* of chaotics might be misanthropes who keep putting themselves ahead of the greater purpose we could achieve with proper societal structure and leadership. But as the much-lamented SRD reminds, chaotics of all stripes think freedom best enables people to reach their potentials. One need not agree with this precept -- and I have many friends from both "sides of the aisle" who don't -- to see that it is neither irrational nor mercenary.