Complex sentence: At some point the vine spread eastward towards the Drôme and Isère regions, for it was here that the variety likely came in contact with the Savoie wine grape Mondeuse Blanche where the two varieties created a natural crossing that became the international variety Syrah.
Split into simpler sentences: At some point the vine spread eastward towards the Drôme and Isère regions. It was here that the variety likely came in contact with the Savoie wine grape Mondeuse Blanche where the two varieties created a natural crossing that became the international variety Syrah.