You’ve just signaled you don’t understand Star Wars’ plot, prepare for a deluge of explanations.
In short, Anakin was emotionally unstable during his battle against Obi-Wan. Under normal circumstances, he’d wipe the floor with his master. In the making of accounts and Star War History books, both George Lucas and Nick Gillard (choreographer for all fights before Disneyfication) confirm that Anakin was an equal to Yoda and Sidious at the end of RotS, far surpassing Mace Windu and Obi-Wan Kenobi.
As a fun aside, in the animated series The Clone Wars, we get a glimpse at Anakin’s full potential - the ability to control all of the force at once, even swapping day for night on a whim.