One verse from Now and Then particularly stands out for me: "It's all because of you."
Since the song was written "for Paul," I tend to believe that John was attributing the Beatles success to Paul. I wonder if John really felt this way.
Good to see you back, Loco!
I personally don't see John ascribing the Beatles' success to Paul, at least not in such an extreme way (i.e., "all"). But that's just my opinion. I would be curious to know who and what he is referencing. I would guess—and it's just a guess—he may have been referring to Yoko or Julian. But as to what the referent for "it" is, I'm not at all sure.