Continuity mistake: When Yoda arrives at Korriban, the wings of his starfighter open up when he flies down to the planet. However, in the second shot of him flying down, the wings are closed. (00:01:10)
Continuity mistake: While Anakin and Obi-Wan are talking about Rush Clovis, a droid head Anakin is working on disappears from a table between shots. (00:07:30)
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.