Convert a disfluent question to a proper question. A disfluent question is a question that has some interruptions in it while framing. A proper question is the correct form of the question without any disfluency.
Q: Why did Yuan's successors win control of the rest of the Mongol empire, oops Kublai's successor?
A: 
Why did Kublai's successors win control of the rest of the Mongol empire?