Lord Krishna shows his 𝙑𝙞𝙨𝙝𝙬𝙖𝙧𝙤𝙤𝙥𝙖𝙢 (opulent form) to Arjun (11.9) who saw many faces and eyes, many wonderful visions, divine ornaments and scents, abounding marvels which are glorious and limitless (11.10 and 11.11). The brilliance is like a thousand suns rising in the sky all at once (11.12). Arjun saw the entire universe within the body of the Supreme Being (11.13).
Krishna granted Arjun Divine Vision as he can't see the 𝙑𝙞𝙨𝙝𝙬𝙖𝙧𝙤𝙤𝙥𝙖𝙢 with his own eyes (11.8). 𝙑𝙞𝙨𝙝𝙬𝙖𝙧𝙤𝙤𝙥𝙖𝙢 consists of Krishna's numerous, glorious, multicoloured, and multi shaped forms in their hundreds and thousands (11.5); 𝘼𝙙𝙞𝙩𝙮𝙖𝙨, 𝙑𝙖𝙨𝙪𝙨 and 𝙍𝙪𝙙𝙧𝙖𝙨; many wonderful things that were never before seen (11.6); the entire universe with the moving and unmoving (11.7).
One easy way to look at the Divine Vision is to take it as the granting of a special power by the Lord to Arjun so that he can see the 𝙑𝙞𝙨𝙝𝙬𝙖𝙧𝙤𝙤𝙥𝙖𝙢 . At a deeper level, 'we don't see the world as it is but we see it as we are' because of polarities of pain and pleasure generated in us when senses meet sense objects (2.14). Secondly, the senses and our brain have limited capabilities which prevents us from being able to see two different things as a part of ONE.
Like how a visually challenged person can't perceive light as well as the beauty light brings into our lives, these limitations of senses prevent us from comprehending the unlimited 𝙋𝙖𝙧𝙖𝙢𝙖𝙩𝙢𝙖 and hence Divine Vision is needed. This is nothing but the end of judgements where oneness is perceived around; the end of divisions where others' happiness becomes ours. With Divine Vision, Arjun saw oneness of the entire universe within the body of the Supreme Being. Certainly HIS blessings are needed to attain this vision but these blessings come at the end of our struggle like how Arjun attained it.