Majority of the people misunderstood the Vishwarupa Darshanam, as narrated in Srimad Bhagavad Gita.
When Arjuna asked Sri Krishna to show his Divine form (द्रष्टुमिच्छामि ते रूपमैश्वरं पुरुषोत्तम), Sri Krishna says as follows:
पश्य मे पार्थ रूपाणि शतशोऽथ सहस्रशः।
नानाविधानि दिव्यानि नानावर्णाकृतीनि च।।11.5।।
O Arjuna, forms of Mine, by the hundreds and thousands, of different sorts, divine, and of various colours and shapes.
इहैकस्थं जगत्कृत्स्नं पश्याद्य सचराचरम्।
मम देहे गुडाकेश यच्चान्यद्द्रष्टुमिच्छसि।।11.7।।
Now behold, O Arjuna, in this, My body, the whole universe centred in one including the moving and the unmoving and whatever else thou desirest to see.
The secret of the Vishwarupa lies in the above Sloka, wherein Sri Krishna said:
द्रष्टुमिच्छसि - whatever thou desirest to see.
Sri Krishna never said that I am showing the Vishwarupa to you and that these all comprise my Vishwarupa.
He simply said that "See whatever you want to see - द्रष्टुमिच्छसि".
So whatever Arjuna saw during Viswarupa Sandarsana, it was his own mind's projections and imaginations.
Sri Krishna did not show anything to Arjuna.
Coming to Sanjaya, he was just narrating the dialogues that took place between Sri Krishna and Arjuna. So Sanjaya just heard what Arjuna said but not what he saw.
The vision of GOD, is like projections on a WHITE screen. It will show whatever is projected on it.
GOD will show to the seekers of GOD, according to their maturity of mind and hence their own mind's projections.
To the Gnani, who lost all desires, only ETERNAL HAPPINESS remains, because that is his projection.
It is very subtle and beyond the imagination of the common man.