Bhagavad-gita has been well known all over the world for a very long time, especially in the Western world, but because the subject matter was not discussed by devotees, there was no effect
SB Canto 4
When there is a congregation of devotees, their discussions, questions and answers become conclusive to both the speaker and the audience. Thus such a meeting is beneficial for everyone's real happiness.
Hearing discussions among the devotees is the only means to receive the powerful message of the Supreme Personality of Godhead. For instance, Bhagavad-gītā has been well known all over the world for a very long time, especially in the Western world, but because the subject matter was not discussed by devotees, there was no effect. Not a single person in the West became Kṛṣṇa conscious before the Kṛṣṇa consciousness movement was founded. But when the same Bhagavad-gītā was presented as it is through the disciplic succession, the effect of spiritual realization was immediately manifested.
Sanat-kumāra, one of the Kumāras, informed Pṛthu Mahārāja that his meeting with the Kumāras benefited not only Mahārāja Pṛthu but the Kumāras as well. When Nārada Muni questioned Lord Brahmā about the Supreme Personality of Godhead, Lord Brahmā thanked Nārada Muni for giving him a chance to speak about the Supreme Lord. Therefore questions put by a saintly person to another saintly person about the Supreme Personality of Godhead or about the ultimate goal of life surcharge everything spiritually. Whoever takes advantage of such discussions is benefited both in this life and in the next.
The word ubhayeṣām can be described in many ways. Generally there are two classes of men, the materialist and the transcendentalist. By hearing discussions between devotees, both the materialist and transcendentalist are benefited. The materialist is benefited by association with devotees because his life then becomes regulated so that his chance of becoming a devotee or making the present life successful for understanding the real position of the living entity is increased. When one takes advantage of this opportunity, he is assured of a human form of life in the next birth, or he may be liberated completely and go back home, back to Godhead. The conclusion is that if one participates in a discussion of devotees, he is both materially and spiritually benefited. The speaker and the audience are both benefited, and the karmīs and jñānīs are benefited. The discussion of spiritual matters amongst devotees is beneficial for everyone, without exception. Consequently the Kumāras admitted that not only was the King benefited by such a meeting, but the Kumāras were as well.