How can "The Hot Priest" do this in the second season of "Fleabag"?

Phoebe Waller-Bridge explains this in The Making of Fleabag, a BAFTA TV Session, which RadioTimes reported on:

During the session, Waller-Bridge revealed that Fleabag’s ‘fourth wall’ relationship with the camera is “mirrored” by The Priest’s relationship and ‘fourth-walling’ with God – both feel like they’re respectively being watched and “witnessed” the entire time.

This also served a dramatic purpose:

Waller-Bridge explained, “[Fleabag] has a relationship with the camera the whole way through, and it was interesting to have someone who has a similar thing, he’s mirrored [because] he has God. And she’s witnessed by the camera the whole way through, and in the end, the big question for her is whether or not she can let go of the camera – and he’s witnessed by God the whole time, and is always having to check into that the whole time. And in the end he has the same question, so I just felt like it would be a really good way to mirror each other’s journeys.”

Note that Waller-Bridge also regards the "fourth wall breaking" as something more symbolic, kind of like an inner dialogue:

“I feel like it’s that pressure of being watched, and feeling watched, and feeling like if you’re not being witnessed, does what you’re doing count for anything, does it matter?… She’s constantly grappling with this need for the audience to validate her,” she added, before stating, “It’s a really fraught… relationship.”