Countless skirmishes happened along China-India border since 1962 war. All were settled peacefully by the two countries. China even compromised in the 2017 Dklam standoff incidence. In which both sides confirmed that Indian soldiers entered China's territory by crossing undisputed boundary line.
Why China is so tough this time? There are many reasons. China's being fed up with India's endless harassments could be one of reasons. I think the most important reason is. China realized things are different and complicated this time. It's not about China and India tension as it looks like. India is more like cooperating with US on the "Containing China" strategy. China has sensed that India had made worst choice for China: Joining in US “India-Pacific Strategy”. India created the tension on border at the peak time of US attacks on China. It's definitely not a coincidence. After 6.15 clash, India government immediately banned hundreds of Chinese apps and limited Chinese goods import for "national security"(sounds familiar?) reason.
Many people believe that all anti China measures and India-US cooperations are the results of China-India clash. No. They were premeditated by India. What was out of Indians' plan is, unlike other skirmishes, this time China didn't back off and gave India a firm slap.
For China, it's meaningless to make any concession if it's not pure China-India issue. Because India had joinned in an anti-China gang. It won't stop hurting China's interest until the boss of the gang says "stop". On the other hand, China needs to fight back. It's not wise to directly fight with US, the boss of the gang. US is too powerful and China's biggest customer. Hitting the pawns is the best choice for China. We have seen how China punished Canada, Australia and of course India while making deals with US even though we all know US is one where the problems came from. It's all logical.
Lesson for Vietnam and other countries. Having issues with China is not a big problem. China overall is a soft and tolerant country. But you have got to keep distance from US. Once you become a pawn of US, you will see a tough China.