I think this supposed popularilty is much more with the media and far left than with Catholic rank and file. I’m not suggesting he is unpopular but I see no reason to believe that he’s any more popular overall than the Pope who preceded him.
What I see is that Pope Francis is simply preaching what his favorite saint, Francis of Assisi once said: “preach the Gospel always, but when possible, use words.” It all comes down to preaching the Gospel with your everyday living.
At least he comes from the new world which is a first.