Why didn't Zhao Tuo return to Qin's aid and establish himself as king in Lingnan? What were the benefits of doing so?

We must first objectively and subjectively analyze why Zhao Tuo did not save Qin and why he chose to make himself king.

The first objective reason was Zhao Tuo’s strength at the time. When the Qin army conquered South Vietnam, its leader was Ren Xiao, and Zhao Tuo was just one of his lieutenants. Later he served as the magistrate of Longchuan County, Nanhai County. Ren Xiao, who was aware of the crisis in the empire in the later years of the First Emperor, had a more keen judgment on the situation after the Second Emperor came to the throne. He was in poor health at the time, so he made a strategic arrangement for Zhao Tuo, who he relied heavily on, to segregate himself and wait and see what would happen. After Ren Xiao's death, the situation developed in the direction he had foreseen. In accordance with this strategy, Zhao Tuo took decisive measures to eliminate dissidents and fully control the local military and political power. On the other hand, he sent troops to guard the key passes between the Central Plains and South Vietnam to prevent the war from spreading southward. Despite this, he was still in his infancy at the time, and his actual control and military strength were still very limited, so he could not gain any advantage by going to the Central Plains. This is a decision based on your own strength.

The second objective reason is that Lingnan is too far away from Xianyang, and the water far away cannot quench the thirst nearby. At that time, transportation was backward and the army was marching very slowly. The war situation is changing rapidly. Maybe Zhao Tuo's army is still on the way and Qin will be finished. When the time comes for him to be alone in a foreign army, it will not only be a question of embarrassment or not, but also a question of whether he can survive and how he can survive. It's distance that determines the decision.

The third objective reason is that if you want to go quickly from Lingnan to Xianyang, you need to pass through the Chu region. It took the entire life of the First Emperor, so the capital of Chu was never fully naturalized. Now that Xiang Liang and Xiang Yan are the leaders of Chu rebels against Qin, Zhao Tuo borrows his old Chu and says that he wants to go to King Qin to save Qin. What do the people of Chu think? Will they get through? It's reality that determines the decision.

The fourth objective reason is that the general trend of the world is destined to destroy the Qin Dynasty, and the mere struggle is like a mantis trying to control the chariot. The world has been suffering from the Qin Dynasty for a long time. Guilin, Nanhai and other places are also counties and counties of the Qin State. It is said that there are intact eggs under the cover of the nest, and their lives are probably in dire straits. Zhao Tuo still has to listen to whether he is willing to save such a Qin country and whether it is worth it. What is the public opinion of the people of South Vietnam? The whole country was resisting the violent Qin Dynasty. It was obviously not a wise choice for Zhao Tuo to foolishly go to Qinwang. This is a trend-driven decision.

The fifth objective reason is that instead of abandoning South Vietnam and returning to the Central Plains to participate in the melee, it is better to firmly maintain South Vietnam under the Central Plains civilization. No matter who unifies it in the future, South Vietnam will still be the territory of China, and it can be regarded as living up to Qin Shihuang and the Central Plains. The sacrifice of millions of Qin troops. Of course, this does not mean that Zhao Tuo is so noble, but objectively it does play this role.

Subjectively, Zhao Tuo did not want to go into danger alone to save Qin.

One of the reasons is that the person Zhao Tuo has feelings for is the First Emperor, and he has no feelings for the Second Emperor and Zhao Gao and others. He does not have to take risks for a son-emperor he has never met.

The second reason is that the current ruler is a treacherous minister like Zhao Gao who rejects dissidents. Zhang Han's experience of being framed by Zhao Gao is still vivid in his mind. Of course, Zhao Tuo would not be stupid enough to become Zhang Han's second.

The third reason is that it is better to have a chicken head than a phoenix tail. In troubled times, there is no place for heroes. Occupying Lingnan, Zhao Tuo changed from a small Longchuan order to the actual lord of Lingnan and a prince. Whether it is an individual or a family, it is a good thing.

The fourth reason is that you can preserve your strength at the right time, and you have chips for self-preservation and development. This was also a bargaining chip for him to negotiate with Emperor Gaozu of the Han Dynasty and Emperor Wen of the Han Dynasty.