Continuity mistake: When Krell is getting in Fives' face about who is going to take the blame for Fives and Jesse disobeying orders, the markings on Jesse's armour are missing. (00:21:21)
Character mistake: When Jesse says that he's "really not liking this", Fives calls him Hardcase when he responds with "don't get an itchy trigger finger." (00:15:35)
Continuity mistake: When Fives is telling Rex he, Jesse and Hardcase are going through with their plan, Jesse and Hardcase switch places. (00:12:26)
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.