How is prayer valid in the Prophet's Mosque when the grave of the Prophet, may God's prayers and peace be upon him, is within it?

The ruling on praying in a mosque that contains a grave, the prohibition of building mosques over graves, and burying the dead in mosques, as well as the refutation of the argument based on the presence of the Prophet’s grave inside the mosque, have been previously explained. Among the wisdoms behind the prohibition of building over graves is to avoid imitating the People of the Book in taking the graves of their prophets and righteous people as places of worship, and to avoid exaggeration concerning the righteous, which could lead to their worship. The Prophet (peace be upon him) warned against taking his grave as a place of celebration ('Eid), and he supplicated to Allah not to make his grave an idol to be worshipped. Allah answered his supplication, protecting him from allowing worshippers to face his grave during prayer. For this reason, Muslims went to great lengths to block any means to this end regarding the Prophet’s grave: they raised the walls of his tomb, sealed its entrances, and made them encircling his grave. Then, they built two walls from the northern corners of the grave, diverting them until they met at a triangular angle from the northern side, so that no one could face his grave.