Why was there such a big gap in the war against Tubo in Tang and Song Dynasties?

In the Tang Dynasty, Tubo was unified and the Tubo Empire was established. It mainly invaded the Tang Dynasty when it declined after the Anshi Rebellion. During the prosperous Tang Dynasty, Tubo was completely annihilated in a stone castle battle in the Tang Dynasty. At the end of the Tang Dynasty, Tubo split, and the general Zhang Chaoyi at the end of the Tang Dynasty put down the Tubo royal aristocrats who were almost defeated by the whole western region. Only one Tubo department was destroyed in the Song Dynasty, which was completely different from that in the Tang Dynasty. Let the Tubo Empire fight the Song Dynasty, and the Song Dynasty is estimated to have perished long ago. Zhang Chaoyi also asked the Tubo ministries to pay tribute to the Tang Dynasty year after year, and made Gaochang Uighur Khan, King Khotan, Kara Khan and Tuguhun Queen Wang Xiangdong as grandfathers of the Tang Dynasty. It accelerated the division and decline of Tubo ministries. Can Tang Tang Tang win in the joint confrontation between the three major forces of Tubo Uighur Nanzhao? The Emperor of the Song Dynasty licked the shoes of the Three Kings a long time ago. After being killed in Song Liao War, the Song Dynasty did not subdue Yanyun 16. Thousands of soldiers and civilians also died. Signed a Buddhist temple alliance that humiliated the country, and now the annual compensation is equivalent to several billion. Not to mention that the two emperors were later captured by the rulers, and Jingkang, the concubine queen of the Song Dynasty, was humiliated by the Jin people. When the Liao Dynasty was about to perish, Song and Jin jointly attacked and destroyed Liao. Song Jun still couldn't defeat the remnants of Liao country stationed in Yanyun 16, and finally exchanged millions of gold for Yanyun 16. On another occasion, the 16 envoy led by Li Gang set out from Song Jun in 2000, when it was not a regular army. 2,000 people were almost wiped out, and 16 Jin people "escaped" back to the Jin Dynasty unscathed. At the end of the Southern Song Dynasty, the Yuan army slaughtered people in several big cities in the Song Dynasty, and the number of casualties was several times that of the Tang Dynasty. At the beginning of the Tang Dynasty, Songzan Gambu invaded Songzhou, and nearly 200,000 fan troops were almost wiped out by 20,000 Tang Jun. Songzan Gambu survived by making peace, paying tribute and kissing. Because of Zhang Yichao, one of the two major Tubo regimes, the head of fear and heat enveloped the cities of the Tang Dynasty; Because of Zhang Yichao, the female servants of one of the two Tibetan regimes are not only exhausted, but also angry with themselves. Because of Zhang Yichao, Tubo lost its sovereignty over Hehuang in Qinghai and the Western Regions. Because of Zhang Yichao, Tubo was completely divided into hundreds of regimes. Although the hands of the late Tang God of War were covered with the blood of millions of Tubo soldiers; But his life must be legendary.