Leadership is something that nobody gets on demand instead it comes inherently with leaders as rewards. Sir Aurobindo, Swami Vivekananda and Lokmanya Tilak were the few leaders till 1920s who stirred India with their deeds powered equally with the words. After the death of Tilak, that leadership came naturally to Gandhi, who already had lead few Aandolan's (movements) such as Champaran then Khilafat and in both the movements he showed the way by example. India that time needed the same - a man who could show the way staying alive. Ambedkar, a child born and grown up under the curse of Untouchability, struggled whole life to get out of it.
(I tried hard not to oppose Ambedkar, as the conditions he faced, it was natural for anyone to return with the revenge mindset.... but only the curses don't create legends but people who come out of this...with..with free mindset, & he could never be free, he even forgot those Savarna Hindus who helped him in completion of his too costly education. The scholarship he got was tiny w.r.t. whole cost, during his stay at various places, that they paid without asking for payment, when he made it very clear that he was not a social worker.)
In the history of India, 'There is not one instance, not one single, solitary instance in which Ambedkar participated in any activity connected with that struggle to free the country ...at every possible turn he opposed the campaigns of the National Movement, at every setback to the Movement he was among those cheering the failure'. - (Worshiping false Gods). He was one who was neither near to Bhagat Singh nor Gandhi nor Gurudev nor Motilal Nehru, if anyone to whom he was near to it was Britishers. For instance take this.....B R Ambedkar writing on 14 May 1946 to a member of the (British) Cabinet Mission, A V Alexander.
"All me to say that the British have a moral responsibility towards the scheduled castes. They may have moral responsibilities towards all minorities. But it can never transcend the moral responsibility which rests on them in respect of the untouchables. It is a pity how few Britishers are aware of it and how fewer are prepared to discharge it. British rule in India owes its very existence to the help rendered by the untouchables. Many Britishers think that India was conquered by the Clives, Hastings, Coots and so on. Nothing can be a greater mistake. India was conquered by an army of Indians and the Indians who formed the army were all untouchables. British rule in India would have been impossible if the untouchables had not helped the British to conquer India. Take the Battle of Plassey which laid the beginning of British rule or the battle of Kirkee which completed the conquest of India. In both these fateful battles the soldiers who fought for the British were all untouchables..." further in parliament, "Prime minister, permit me to make one thing clear. The depressed classes are not anxious, they are not clamorous, they have not started any movement for claiming that there shall be an immediate transfer of power from the British to the Indian people.... Their position, to put it plainly, is that we are not anxious for transfer of power from the British to the Indian people.... Their position, to put it plainly, is that we are not anxious for transfer of political power...."
In fact, there are plenty of writings like this those accentuating him as demagogue. He was among those who were actively writing against whatever Gandhi was doing but very few times came face to face which Gandhi wished. whenever he came, he came with the problems like he had to give Rs. 7 as rent and all....Gandhi, despite all the odds what he created; he did help him.
Quoting him (September 22, 1932, Gandhi to Ambedkar)
"I am not at all angry with you. When you use derogatory and angry words for me, I tell myself that I deserved that. I will not get angry even if you spit on my face. I say this with God as witness. I know that you have drunk deep of the poisoned cup. However, I make a claim, which will seem astounding to you. You are born an untouchable but I am an untouchable by adoption. And as a new convert I feel more for the welfare of the community than those who are already there . At the moment I have before my eyes the dumb untouchables—unapproachables and unseeables—of South India. I am scrutinizing the scheme to see how these people will be affected by it."
It was only because of Gandhi that Ambedkar could achieve this position other wise, Vallabhbhai patel, Maulana Abdul Kalam, Madan Mohan Malviya were in no mood to give any space to him within Indian Government.
If there is a cockroach in your room, what you do?
You either kill it or throw it away from the room. Will you change the room saying that room was never clean and there might be more cockroaches inside?
In his long experience, Gandhi could feel that making separate religion/election won't solve the problem. it's the mentality of people that should change within society. He could see that those Savarna Hindus do behave muslims too as untouchables. Gandhi in his Ashram kept several untouchables along with the Savarnas - to break the myth by setting an example. Opposite to that, Ambedkar was in a mood to make a separate religion for these people, so that he could be worshiped as Buddha, Mahavir or Christ in future...
but they didn't incarnate with any feeling of avenge or revenge.
After Poona pact, when it became clear that there won't be any separate election/religion for untouchables. 14 October 1956, Nagpur, Baba Saheb Ambedkar along with his two lacs dalit followers took 22 Oaths changed themselves into Bauddhism. The 19th one was:
"I thereby reject my old religion, Hinduism, which is detrimental to the prosperity of human kind and which discriminates between man and man and which treats me as inferior".
Ambedkar always represented himself as a leader of untouchables but on 14 October 1956, only two lacs people out of 20 crore, gathered at his recall. In 1952 elections, his own party could manage to win only one seat out of 454 (as per my knowledge). He lost even his own seat. He was the one who whole-heartedly supported the partition that took away 14 million lives, without feeling the heat how did it affect untouchables at large. He thought about untouchables not untouchability. To Gandhi, people were never untouchables but it was untouchability that was needed to be cured. Perhaps is the reason, in '52 election Ambedkar was shown the door, as he didn't do any commendable development work in the wake of untouchability. After getting nowhere, he turned to Buddha with the oath written above which is in against of the Noble eight-fold paths of Buddha.
There is much common between Ignorance and knowledge as both begin from the same point and end at the same point. The actual difference lies in their paths and deeds.