I want to know the answer to the following question:
What year was the Sakya viceregal regime eradicated?
All the background I'm provided with is that "The Mongol Yuan court was forced to accept him as the new viceroy, and Changchub Gyaltsen and his successors, the Phagmodrupa Dynasty, gained de facto rule over Tibet.". Is that enough to answer the question?
Answer: no