Complex sentence: While their lives may have been spared due to popular demand, Phocas likely viewed Priscus himself as the culprit, and seems to have started viewing his son-in-law as a potential rival.
Split into simpler sentences: While their lives may have been spared due to popular demand, Phocas likely viewed Priscus himself as the culprit. He seems to have started viewing his son-in-law as a potential rival.