Complex sentence: Telavi re-gained its political importance in the 17th century and by 1762, it turned into the second capital (after Tbilisi) of the united Eastern Georgian Kingdom of Kartl-Kakheti.
Split into simpler sentences: Telavi re-gained its political importance in the 17th century when it became a capital of kingdom of Kakheti. By 1762, it turned into the second capital (after Tbilisi) of the united Eastern Georgian Kingdom of Kartl-Kakheti.