The caste system in Hindu society has been a part of cultural traditions which was based on the theory of division of labour according to ability and aptitude for work. Even now employers place their new recruits to different type of work on the basis of their ability and aptitude. Manusmriti is a text book of the theory of work placement. Later on, untouchability crept in as an unwanted intruder.
I do not agree with the statement that Dr Ambedkar was against caste system. He was in fact a strong advocate of caste system, otherwise he would not have proposed caste based reservations. Caste based reservation in jobs and political system has strengthened caste system. Is it not that reservation is a caste based discrimination? I'm of the firm belief that so long as caste based reservation is in place, the caste system will get stronger and caste based discrimination will get a boost. The talented young men who are the victims of reservation would react in their own way.
As far as conversion to Buddhism is concerned , I feel it is a strategy to blackmail the society and the government. Nobody is really converting to Buddhism. As far as I understand, Buddhism is a very good religion which does not believe in casteism. But, those who claim to have been converted to Buddhism do not forego their caste identity because they do not want to leave the benefit of caste based reservation. So, nobody is truely converting to Buddhism. It is simply a political stunt.