Yudhisthira is the ultimate sattwic man, and like all righteous men lives in the self-sufficiency of his intellect. He governs his life by the Shastra and the rules of right and wrong as enjoined by the books. It is this that prevents a higher spiritual opening.
Arjuna, on the other hand is a Rajo-sattwic person who though familiar with the Scriptures and the texts is yet seeks for the higher direct Guidance of the Divine. He is able to see that the scripture and its rigid doctrines of right and wrong are unable to resolve his internal conflict and hence he submits to the Divine Guidance which is always greater than the scripture. It is this humility, this seeking, this complete faith and surrender to the embodied Divine that makes him qualify for receiving the Gita. The Viswaroopa is further revealed to him as part of the great teaching since he is now ready to fight. He is now no more shrinking from the battle of life. Hence Sri Krishna imparts to him the ultimate truth that it is the Divine who is the sole doer and Arjuna has been chosen to fulfil the Divine Will.
Yushisthira would not be so convinced. He would need a scriptural answer which Bheesma can provide with his reading and experience. Those who live life through a rule book and are proud and satisfied about it miss the higher Divine Guidance that acts in perfect freedom and from a consciousness that is beyond good and evil.
Affectionately,
Alok Da
