Facing the same issues as many other loyalists, for the reasons that:
1, there is no objective gain from winning the tournament. He is not securing the safety of any people, nor making a significant strike against the Blood Raiders. Money can be acquired through other, easier methods; glory or 'demonstrations of power' are better held, he feels, to the actual battlefield than for playing a Blooder's silly game.
2, Esna isn't keen to risk his crew for negligible gain. In the previous tournament, where there was a high chance that the 'team' would hold the field and allow his crew to escape safely (as did happen), he was eager to take part. In this, however, he's putting lives on the line for (as discussed above) little apparent gain.
So, with those two factors in play, Esna's left apparently playing with other peoples' lives for the entertainment of a Raider with no definitive chance of success, nor any real victory at the end. That's not a chance he'll take.