They went to the temple to discover what had happened, and when it was discovered it was Sidious and Skywalker - they set out to kill the sith and cut off the head of the snake. Yoda fails in that mission. His mission wasn't to delay, or challenge Sidious.. it was to end him. That was their stated purpose.
He failed and rather than push the attack more, he gives up the fight. No one stopped the fight but Yoda.. because he cuts and runs after making the determination he can't win. We call that losing when you fail to meet your objective
At that point Yoda concedes defeat and retreats from the planet... to determine another path to resist.