They do not believe that Jesus Christ as known in the Catholic Church must be at the centre of all political and social legislation.
They do not believe that all need 'faith and baptism' for salvation(Vatican Council II, Ad Gentes 7).So to avoid the fires of Hell all need to formally enter the Church,is not more the priority in social and political legislation. Even the popes, cardinals and bishops do not believe in this any more. This is why in Italy the majority of Catholics vote for political parites like the Partito Democratico, Alleanza Nationale etc which do not support the Social Reign of Christ the King.
Instead the popes and cardinals have accepted the New Theology of Rahner and Ratzinger which suggests that there is known salvation outside the Church.This is their view even though there is no known salvation, practically known, outside the Church. Neither has any one in the past seen personally someone saved outside the Church.
Yet this is how Vatican Council II is interpreted. Since there is known salvation of the baptism of desire and being saved in invincible ignorance without the baptism of water, there is no more the dogma extra ecclesiam nulla salus. Since the dogma on exclusive salvation does not practically exist any more there is no more an ecumenism of return.
Since there is alleged known salvation outside the Church it is not necessary that the Social Reign of Christ the King be a priority for the popes and Catholics. People are saved in their religions even if they are not Catholic.
This Rahnerian theology is also accepted by the SSPX and the other traditionalists.
So Catholics today do not feel obligated, in Italy for example, to vote for Militia Christi or Forza Nuova.