1.He did it owing to what he had done with Luke,he had already decided to test him and let him kill Vader. 2.In fact,Vader and Anakin are two different personalities. 3.He didn't want him knowing it. 4.It's all Obiwan‘s fault.
1.Because Yoda wanted to practice Luke's patience. 2.Because the emperor thought Vader has fallen completely and lost his human nature. 3.Because from his point of view, Anakin was killed by Vader and he wanted Luke to kill Vader. 4.I want to ask a question: Can the act that Obi-Wan instigated Luke to kill his biological father really save the galaxy? After all, the emperor also wanted Luke to kill Vader.
我给个不太正常的答案吧...... 1.Yoda has been stucked on that planet for 22 years,alone. 2.Certainly the emperor doesn't want Vader and Luke to unit their strength against him,he needs them to fight each other instead. 3.He does not consider Vader as his former apprentice . 4.Epic.