Were Christians permitted to pray in the Prophet's Mosque, and what is the wisdom behind that?

The report of the delegation of Najran Christians praying in the Prophet’s Mosque is weak, its chain of narration is not authentic, and it cannot be used as proof. It has been narrated through three channels, all of which are not authentic: the first is disconnected and problematic (mu'dal), the second has a ruined chain of narration, and its narrator is abandoned and accused of lying, and the third is disconnected and weak. Such a report cannot be used as evidence for the permissibility of allowing non-Muslims to perform their infidel rituals in mosques, because it is not permissible to condone their polytheism in the houses of Allah; as Allah Almighty says: ﴿And that the mosques are for Allah, so do not invoke with Allah anyone.﴾ (Al-Jinn: 18). Even if the report were hypothetically authentic, it would be interpreted as the Prophet (peace be upon him) conciliating them to win their hearts, and this does not necessitate permanent permissibility. The entry of a polytheist into a mosque other than Al-Masjid Al-Haram involves detail and disagreement, and it is permissible if there is a legitimate benefit with the permission of a Muslim, unlike enabling them to perform their infidel rituals in the house of Allah.