Manhattan, Trump is playing chess, while you're analyzing his moves as if he was playing checkers. He'll do what's in the best interest of the US, period. The poor Kurds are nothing more than speed bumps. It's wrong, and it shouldn't have gone down that way, but what would you have the US do? Leave our 50 - 100 troops in the path of a significant Turkish invasion force? That certainly would have no negative ramifications, for example a shooting war with Turkey.
So, how could the US have prevented this, or even mitigated it to any kind of tactical or strategic benefit for the Kurds? I'm willing to listen and change my position based on new evidence. So let's have it.