But then Krishna's identity makes him the biggest historical Ishvara in Hinduism. His color makes him a more universal and acceptable Ishvara. Moreover, Krishna protects Brahmins and their interests through his words and deeds. Sure, Hinduism and its biggest historical preaching belong to all of its followers in modern times, including to rear castes and outcastes. But no one can question Krishna's Puritanism, idealism and his emphasis on caste dominated Hindu world order.
The fact is that when Islamic rulers invaded India, Rama was reinvented by high Brahmins but the fact remains that Hindus of that time saved themselves because of Bhagavad Gita too and possibly the contribution of this sacred book was bigger in magnitude. Krishna's identity is mostly universal as almost no theist Hindu identity in India and abroad would question Krishna's role in the war of righteousness between the famous Pandavas and infamous Kuaravas.
But the fact remains that the war was controversial since beginning and Hindus are not that comfortable with the war though they are mostly happy about the results of war: evil Kauravas were destroyed and killed by good Pandavas with the help of Krishna. But the fact is that Kauravas were cousins of Pandavas and this fact makes the story a bit tragic. Sure, sage Vyasa, whose grandchildren Pandavas and Kauravas were, has taken utmost care to highlight and portray the positive sides of Pandavas and dark sides of Kauravas throughout the epic. The way it is written very few theists, in fact almost nil, would question the victors and their supporters. Neither would they question the arguments in the winners' favor nor arguments against the losers.
Krishna has great utility in the modern times too. In this ear of proliferation of identity in India, Krishna's dark color and 'not so high' caste makes him a very acceptable Ishvara. Rama is the creator of Brahmins and as per Valmiki's Ramayana he is Kshatriya. The temple movement in Ayodhya in UP has made Rama a political Ishvara and therefore, inadmissible to many people. The same does not apply to Krishna.
Moreover, Krishna is the absolute Ishvara as per many beliefs; the Supreme Being, the Brahman. If one thinks along the upper caste lines then Krishna is the ultimate manifestation of the Supreme Lord and as per a majority Hindu belief, he is the ultimate Brahmin on earth, above sage Vyasa and great Manu. Therefore, Krishna is worshipped equally ardently by upper caste Hindus and backward classes and non-caste Hindus.
I fully understand that Krishna is bigger than Rama if hierarchy is ever tried drawn by learned Brahmins. And I am not trying to divide us Hindus by favoring one deity above another. But this is the reality. The fact is that both Rama and Krishna unite Hindus of all regions though the latter has bigger contribution. In the Sanatana Dharma both have very high significance.
As per noted exponent of Hinduism, Gavin Flood, the main themes of the Gita are: the importance of dharma; dharma and renunciation are compatible: karma should be performed with complete detachment; the soul is immortal and until liberated is subject to rebirth; the Lord is transcendent and immanent; the Lord is reached through devotion by his grace.
Rama created edge and Krishna built on that to provide consciousness to Hindus. But the British imparted maximum consciousness to Hindus if there is consistent and compatible measure applied. The fact is that Sanskrit is almost extinct but English dominates over the vernaculars and Hindi, mostly originating from it. Also independent India is a dynamic and viable democracy?a gift by the British. However, the preaching by Krishna provides modern Hindus an open and inclusive ideology to argue with the rest of the world and prove their usefulness to others. In that sense and in others too Krishna is indeed great and the Lord of Hindus.