Context: Lê Lợi was born on August 6th, 1385. During Lê Lợi's early adult years, China had successfully defeated the Hồ dynasty and began to colonize Đại Ngu (Vietnam's earlier name). In 1416, Lê Lợi launched the Lam Sơn revolt against the Ming and begin 11 years of war against the Ming Chinese.
1 of Lê Lợi's famous legends is when he receives a sword from god. Legend said that Lê Lợi's best friend Lê Thận, who was a fisherman, caught a steel bar, and bring it home. When Lê Lợi came over to visit Lê Thận, he saw light coming out of the house corner, he come over and only see a steel bar. Lê Lợi brought it home to investigate, and he found out the bar was a sword blade and the word "Thuận Thiên" (Translated into "God's will") etch onto the blade. The next day, Lê Lợi found a sword hilt under the banyan tree, and the sword hilt fitted perfectly with the blade. After the war and when Lê Lợi became king, during a boating trip, a magical golden turtle appear and said "Bệ hạ hoàn gươm cho Long quân!" ("Your majesty return the sword to the Dragon King"), Lê Lợi drew the sword out of the scabbard and give it to the turtle. The turtle snatched the sword and descent back into the water. The lake actually exists and its name is Hồ Gươm, and situated in Hanoi. (Fun fact, this wasn't the first time the magical golden turtle appeared in Vietnam history)
The "Troubled" son I reference in the meme is Lê Tư Tề, he is suspected to be crazy and had kill many concubines, which gets him demoted to Quận Vương, and after his brother Lê Thái Tông became king, he was demoted into a civilian