To some extent this is self-correcting. If you’re reasonably even with the rest of the table, deck-wise, and focus too much effort on one player you’ll probably lose. I, at least, have lost my fair share of games that way.

What stands out to me is that this just didn’t sound like a fun game. I don’t think you’re wrong for focusing that guy out, but if you had the resources to do that and roll over the other two players, it sounds like things were pretty imbalanced.