Allahabad is the second oldest inhabited city in India after Benares/Varanasi. Up until the Mughal rule, it was called Prayag/Prayagraj as it was at the confluence of the 3 most important rivers in Indian history – Ganga, Yamuna, and Saraswati, with Prayag meaning “a place of worship”.
Akbar found the city to be of strategic importance and set it up as one of the capital of its 12 constituencies called Subah (the term from which Subahdar/Subedar is derived, equivalent to a district administrator).
Prayagraj was renamed Subah of Illahabas, meaning “the region that is the residence of Allah”.
As such, the name, Allahabad, still is a vestige of the Mughal rule, and it being restored to its original name is a welcome move.
If Calcutta can be Kolkata, Bombay Mumbai, Poona Pune, Mysore Mysuru, Bangalore Bengaluru, etc to reflect the local pronunciation and customs, and to undo the Anglicization of Indian city names, why not Allahabad? Major streets and landmarks have been renamed through the years to remove British/Mughal influence. (e.g. Victoria Terminus (VT) is Chhatrapati Shivaji Maharaj Terminus (CST)). Pakistan has renamed Hindu Bagh to Muslim Bagh, and Krishan Nagar to Islampura. Bangladesh’s capital Dhaka was renamed “Jahangirnagar” during the Mughal empire, but subsequently restored back to its original.