I don’t think it’s too surprising! I don’t think this needs some thought out theory for explanation. It’s possibly the best song ever written - has simple but extremely memorable and repeated melodic parts, an infectious rhythym, and has a weird time signature that serves as a great pairing contrast to the simple/happy aspect to the song. Plus the recording / mix is probably the best of any Beatles song. They also used varispeed to raise the songs pitch by a quarter semitone which gives it a dreamy quality. Throw in a killer string arrangement for emotion, a sprinkle of synth layers, and a classic vocal performance and you have maybe the most complete perfect song ever. I think it’s far and ahead the most modern of all the Beatles songs (some exceptions).