Complex sentence: From that time no serious effort was made by the Byzantines to regain possession of the country, and it would appear that the Arabs were actually assisted by the Copts, who found the Muslims more tolerant than the Byzantines.
Split into simpler sentences: From that time no serious effort was made by the Byzantines to regain possession of the country. In all of this it would appear that the Arabs were actually assisted by the Copts, who found the Muslims more tolerant than the Byzantines.