Continuity mistake: R2's squad of battle droids has three members. Yet in the climactic fighting of the previous episode, one of the droids was shown getting destroyed.
Continuity mistake: When Ahsoka is boarding the rescue gunship, her normally green lightsaber has a blue blade. (00:18:00)
Answer: I guess that 1) the King assumed that Ventress' droids were meant to capture the Jedi, not kill him outright. When she yells at OOM-224 to shoot Yoda, she evidently failed that expectation. 2) Sending out a bunch of Droidekas after it is plain that Master Yoda has clearly won is not a sign of good sportsmanship, either.