Srimad Bhagavad-Gita :
Chapter-4. ( Jnana-karma-sanyasa-yogam )
Slokam-2. ( Following the first slokam, the great knowledge transfer from Lord Krishna-to Surya-toMsnu-to Ikshaku- Sri Krishna continues in this slokam this great knowledge transfer chain was broken in the course of time, and we lost the great treasure of knowledge )
parantapa = O, Arjuna;
evam parampara-praptam = this way acquired by generations (in succession);
imam rajarshyah viduh = this yogam (science) Raja-Rishies ( Saintly Kings ) too understood;
sa yogah mahata kalena = that yogam (Knowledge) in the long run / in the course of time;
iha nashtah = here (we/ to us ) lost.
Thus was transmitted from Lord Krishna a distinguished parampara or disciplic succession from illustrious father to illustrious son. This knowledge was passed onto the saintly kings and royal sages like Nimi and Sagara; but its origins are without beginning because its roots are in the eternal Vedas. By great efflux of time and degradation of human intelligence limiting qualified recipients this great knowledge disappeared into oblivion due to a break in parampara causing a discontinuation of the tradition in this world.
This eternal yoga or the science of the individual consciousness attaining communion with the ultimate consciousness. The saintly kings such as King Nimi as well as royal sages at court all were knowledgeable of this yoga as instructed by their ancestors Ishvaktu and others. The reason why the kings of the day were not knowledgeable of this yoga was because it was lost to parampara or authorised disciplic succession due to great passage of time.
This supreme science was thus received through the chain of disciplic succession, and the saintly kings understood it in that way. But in course of time the succession was broken, and therefore the science as it is appears to be lost.
This yogam which was continued by the Guru (Rishi) Sishya parampara, sustained by this tradition maintained for long, meanwhile this tradition had to face the bad effects of time. In the ancient history this knowledge was easily available for the benefits of human race.
Later this golden period came to end and the birth of dark yugam "adharmam" took place.
The demonic materialism in that period, because of burden of own adharmic deeds, the people were in suffocation ( of this burden ), when this happened some or other Mahatma took birth, began to guide them in right path and gave the cultural nourishment.
The yugam of Mahabharatham and Lord Krishna belonged this period, hence Lord had to mention the loss of great tradition in this slokam, read and study this slokam with the previous one too.
To be continued ..