When the communists took over mainland China, the place where the tradition was invented, they made the best of the art form to "criticize feudalism" and "advocate new ideas." Therefore, they've cultivated many talented actors and sorted out the theory and history of comic dialogues.
原產地既然在大陸，共產黨統治後更善用相聲這項白話絕活兒來「批判封建」、「宣傳新思想」，因此培養出許多人才，也整理出相聲的理論及歷史。