Worth the risk, imo. If they drew today and lose vs Spain in the last round, they are 100% out. If they win 1:0 today, and they did, and they lose vs Spain in the last round, they might be easily out again on goal difference.
Sure, 1:0 is better than 0:0, but since it might easily turn out in the end that 1:0 will be the same as 0:0, Chile wanted the 2nd which was gonna put them in a much much better situation.