At first, when Michael is in Sicily and meets Appolonia, there is no question that he was indeed struck by "the thunderbolt." He instantly fell in love with her. Combine that love with the fact that during Michael's stay in Italy, he began to learn about his culture and his roots. He returned to his family origins.
Absolutely. Starting with "I'm with you now, Pop," Michael started aggressively erasing his former distance from his family, his roots and his "destiny." I don't doubt that the thunderbolt hit him. But the way he courted and married Appolonia seemed an aggressive assertion of his Sicilian heritage.
Remember, it was not like he ran to Kay as soon as he returned from Italy. He waited a year or more. He only reached out to her after realizing that his first love would be the perfect American wife that he would now need to help legitimize himself and his family.
I believe Michael loved Kay, in his own way. But that way wasn't very warm and passionate. The courtship scene (with Michael looking like a pint-sized banker in that Homburg hat) sounded more like a business negotiation than a proposal of marriage. Not for nothing did Kay ask, "Michael, what do you want from me?"
