But you don't need to be particularly religious to name your children
Giovanni or
Paolo, they just happen to be very common male names, very much like
John and
Paul in the English-speaking world. It's really not the kind of name that makes you think "oh, that kid's parents must be religious."
Nor does
Christian nowadays for the matter.
40 years ago or now, it's more likely that if someone gets named
Giovanni or
Paolo it's to honour a grandfather who had that name, rather than to express a religious belief.
And since Italians don't use surname-derived names, and made-up names or "exotic" names tend to be rare as well, the vast majority of names used by Italians, whether they're religious or not, are technically saints' names or Biblical names, by virtue of being traditional Western names.
I don't know any
Christian's because the name isn't so common for my generation, but I know a couple of
Cristiano's and I doubt any of them came from particularly religious families, nor are they religious themselves. I suspect their parents picked it just because they liked it.
There seems to be this myth of Italy as a country of ultra-devout Catholics, but it's really no longer the case, if it ever was. Religious practice is dwindling like in other places, and while the majority of the population is nominally Catholic in many cases they're not religious at all, really.
Formerly Known as Murasaki