When did Charlemagne’s empire flourish?

The heyday of the empire of Charles the Great was in 771, when Charles himself became ruler, who created the first European state. His power could only be compared with the Roman Empire, but limiting the flourishing of Charles’s empire to one year would be wrong. In 800, when Charles became emperor, the flourishing of his empire did not stop there.
With his reign, the empire reached many heights with territorial gains, as well as with an internal political situation.
in 90, Charlemagne began transforming states with the army, the peasantry, and science, which took a decade.
But the state he created turned out to be short-lived and disintegrated under his successors. According to dates, it was 800-814.
Since, in 800, Pope Leo ||| in Rome, Charles placed the crown on his head. It is generally believed that the heyday of Charles’s empire comes in the same year.