[Antoninus]

If they had balanced it with adding “How Great Thou Art” or similar, it would’ve been a smart move.

Recall that Biden is a cultural Catholic and is attempting to garner Catholic votes that way. Trump needs those votes to win. He's already got the evangelical vote locked up. The smart thing to do is to swallow your disdain for Catholicism and enjoy the moment.

[Albion Wilde]

I agree—he was appealing to the Catholic voter. That said, I don’t think the choice of Ave Maria was entirely cynical; it may have been suggested by Melania, with her elegant European tastes.