So, let me get this straight. Joseph notices that Mary is pregnant. Joseph confronts Mary about it. And Mary replies: err, hmm, I know, the angel of the Lord came down and impregnated me. We’re going to have the child of God. And Joseph is like: okay, cool.
Mary: I was raped by an occupying Roman soldier who impregnated me, my family will murder me…
Joseph: we’ll say god made you with child and we’ll get married, fixed.
At least that’s my theory on the whole thing
When presented with a fantasy, every theory is plausible.