Wot? His company gave him a counteroffer with the attitude that accepting their offer would be unethical?
The problem with this is that the people making the counteroffer often feel they are doing so, effectively, at gunpoint: give me a bag of cash right now, or lose a key cog in your machine. "Nice company you've got there. Sure would be a shame if something were to... happen to it." So they are often made grudgingly, which leads to bad feelings. And if they are accepted the bad feelings go deeper, because now the people making the counteroffer feel like you put one over on them. So paradoxically, taking their counteroffer can hurt your relationships with those people pretty deeply, while rejecting it can keep them stable or even improve them -- when you walk away, they can interpret it as you choosing not to put one over on them.
None of this makes any logical sense, of course, but we're talking here about emotional decisionmaking, which has very little to do with logic.
Perhaps it would make more sense if it said "because he hadn’t played games and hadn't acted unethically"
There is no such thing as "unethical." There is always an ethic involved unless the person is acting completely without reason and randomly, such as when they are insane (and even then there is probably still some kind of reason in their mind). In this way, a person conducting themselves in an "unethical" way is likely on the verge of death or incarceration.