Final answer:
The Pope did not annul Henry's marriage to Catherine of Aragon because it would weaken the Church's position and anger Catherine's powerful nephew, Charles V of Spain.
Step-by-step explanation:
There were two main reasons why the Pope did not annul Henry's marriage to Catherine of Aragon. Firstly, Henry argued that his marriage to Catherine was invalid because she had first been married to his late elder brother. This violated Catholic Church law which prohibited the marriage of close relatives. However, the Pope did not want to reverse a previous decision and weaken the Church's position.
Secondly, Catherine's nephew, Charles V of Spain, had recently taken control of Rome, the papal seat of power. The Pope, Clement VII, did not want to anger Charles V by annulling the marriage. Therefore, he refused Henry's request for an annulment and maintained the validity of the marriage.