Why did Bramante's plans for the St. Peter's Basilica never come to fruition?

C. The pope died and political unrest followed

Emperor to destroy this burial place to make way for the planned church. When Constantine came to build the first basilica to St. Peter he simply filled in the road way and small lanes between the Ancient Roman tombs and mausolea and leveled off the top of Vatican hill, thereby keeping the necropolis intact, albeit inaccessible. St. Peter was buried towards the top of the hill and the layout of the new church was to be oriented around his tomb. Once this level platform had been created, the new basilica was constructed on top of it. Later, in the 16th and 17th century when the new basilica was planned it was decided to use the lower section of the walls, and much of the foundation structure from Constantine's basilica as a base for the building.

The second level, which was originally floor level in Constantine's basilica, then became the grottos or burial place for popes, kings and queens dating from the 10th