Why did liu bang adapt a political outlook somewhere in between confucianism and legalism?

After Liu Bang seized power, he re-centralized China based on the Qin Shi Huang model. He gradually replaced the original vassals, granting their lands to their relatives. Since the economy had been devastated by war after the death of the last emperor of the Qin dynasty, it reduced taxes, developed agriculture and restricted public spending. However, it restricted trade with heavy taxes and legal restrictions on traders.  

Under his reign Confucianism gradually replaced the thinking of the legalists; it supported the Confucianist scholars during his government, while the severe laws of the legalists diminished in influence. Emperor Gāozǔ's efforts laid a solid foundation for the four hundred year long reign of the Han dynasty.  

Legalists especially highlighted pragmatism as the basis of the law. The first emperor, Qin Shi Huang, used it to weaken the power of feudal lords, conquer and unify belligerent states into a single empire, create thirty-six administrative provinces, and standardize the writing system.

In later dynasties, legalism was discredited and ceased to be a school of independent thought. However, ancient and modern Confucian observers of Chinese politics have argued that some legalist ideas merged with conventional Confucianism and still play an important role in government. "Confucianists on the outside and legalists on the inside."

they wanted the u.s. to fight on the side of the central powers.