Why was there so much political …

The rivalry between the Pallavas and Chalukyas originated because they sought to control the same area, the eastern part of peninsular India consisting of present day Andhra Pradesh and Northern Tamil Nadu. Since they were neighbouring kingdoms in a rich and fertile region, it was natural that they were fierce rivals. Both kingdoms coveted the territory of the other.
The rivalry started with the attack on the Pallavas by Pulakesi II, the greatest Chalukya ruler, in 620 AD. He was attracted by the prospertity of the Pallava kingdom, particularly it capital, Kanchi. He defeated the Pallavas. This was then followed by an attack by the Pallavas on the Chalukyas in 642 by Narasimhavarman, who completely destroyed the Chalukyan capital of Vatapi.
 This cycle of attacks and revenge attacks continued throughout the seventh and eighth centuries.