Worse than quitting on your team?
Yes, Number Two is certainly the best player the Spurs have ever traded away. But the best ability is availability, and Number Two made it clear that he was not going to be available. At that point he had zero value as a player, his only value was as a trade chip.
Given the general perception that he was going to walk away from any non-LA team he was traded to (which was proven to be correct), not many teams were going to give up long-term value for a 1-year rental.