The purpose of the Bhagavad-gita can be preached only when it is taken up by real devotees of Krishna the Personality of Godhead.
One of the real devotees of Krishna was Arjuna during the appearance of Lord Krishna and as such the parampara of the Bhagavad-gita, which was broken prior to the occurrence of the battle of Kuruksetra, was reestablished at the battlefield and Arjuna was authorized to understand the purpose of the Bhagavad-gita. We should not miss this important point if we are serious about preaching the gospel of the transcendental literature.
As such it is understood in the beginning that one who does not follow the foot prints of Arjuna, cannot enter into the mystery of the Bhagavad-gita and therefore nobody can preach the gospel of Geeta without knowing its mystery.
There are thousands and one scholars in India and abroad but very few of them have followed the foot prints of Arjuna except the Vaisnava Acaryas such Sri Ramanuja, Sri Madhya, Lord Caitanya, Sridhara Swami, Madhusudana Sarasvati, Vishvanatha Cakravarti, Baladeva Vidyabhusana, etc. and many others who have followed the bona fide Acaryas.