They manage it because their "Catholicism," such as it is, is pretty much that of a substantial segment, if not a plurality, of American Catholics. CINOs in the electorate help to elect CINOs to office. Over time, that has become the most visible obstacle to the Church's effort to evangelize the culture. How can there be a "Catholic" witness in the public square when so many powerful Catholics are CINOs, just like so many other Catholics who help to elect them?
Nothing will change unless the clear majority of American Catholics actually embrace Catholicism in reality, not just as an inheritance from which they can pick and choose to suit their inclinations. In other words, Catholicism for them will have to become faith rather than opinion. Then we'll get lots more Bobby Jindals—which is exactly what we need.