Board Thread:Questions and Answers/@comment-31654305-20190517091510/@comment-27274306-20190521073309

That is because he wasn't awakened yet as noted by the DK and he keeps growing stronger as Merlin noted. He was far from his prime during his fight with Escanor and he was playing around and far from being serious as revealed by Zeldoris later on.

You should keep reading the manga.