Well, for one thing, Christianity is basically a Jewish religion, in terms of its ethics.
I'm not sure there is a return to religiosity, it may be that what Medved is observing is a reaction by most Americans to the increasing leftist attacks on Christianity.
I think he's on to something. Poll after poll shows that college students are becoming more interested in traditional religious expressions (whatever faith they identify with).
The megachurches are bleeding the mainline churches dry and in turn, they are feeding large numbers of people into traditional churches like the PCA and the CLC. "The Passion" was deeply religious, not 'spiritual', and people couldn't get enough.
I think we may yet live to see a period where it's "cool" to be religious.