They have nothing to lose and but more to gain by promoting St. Pius X, since it keeps up appearances, and they would give themselves away too much if they were too silent or show some kind of disgust toward the saintly pope. If modernism is not mentioned at all, they would want to hide it, of course, but on the other hand, if they do mention it, they may just explain it away and consider it a thing of the past since they being modernists think faith and morals can change.