Understanding the Caste System

Caste system we always see from "English" point of view but i will try now to provide alternative theory. We have been hearing so much negative about caste for so long. Our Indian culture has been abused just because of this thing.
Mainly it was started by Christian missionaries and those who were educated from those schools which were funded/managed by them.
But no one from our intellectual society took the pain to do the research why this system started in Indian society? What was the significance of this? How come it could able to survive in Indian society since rigvedic period?
Had it been so worse, why it had not been disappeared though Indian society were subject to attacks from outside? For the last 1000 years, we have been attacked/persecuted by peoples from western side of our nation who were primarily Muslim and who forced Indians to adopt islam religion on the force of sword (as said by contemporary muslim historians).
Later on it was a period of Christian missionaries who landed here after baptisizing Africa and America. With the help of European power, they tried to convert peoples into their religion.
So there was open opportunity for so called suppressed lower caste peoples who could have left their ancient religion/customs but they didn’t??
Now the question comes, why these foreign powers could not able to convert this land a Muslim land or Christian land despite there was a significant portion of those peoples who were from lower caste.
To answer this, we will have to be open mind and will have to look on Indian history from neutral point. He will have to leave his missionary school thinking behind.
“Pursuha Sukta” of rigveda talks about society based on four varna “castes”. Again in “shree Bhagvad Geetha” lord shri Krishna says to Arujn :
“chatur varnam mayam shirstum, guna karm vibhagsha” means these four varnas are created by God and these are based on guna (qualities) not on birth.
Gradually it became birth based because usually a child learns that profession which he sees in his home from child hood.
Just because of this caste system, every one was employed. Every one was self dependent.
When British peoples came, they attacked on this system. They stopped cloth making, shoe making and lots of other profession in which many peoples were employed. They started to import these things from England and forced Indians to purchase. Now a large section of society became job less and lost their importance.
As it happen in one’s house that if some one looses his importance, other family members start to neglect him. Same happened with Indian society also. Peoples who were able to occupy status in new british clerical system, they started to neglect those who were job less and which became lower caste society later on.
In our history, we never witness any dispute/war based on caste because it was meant to give employment to every one. There are so many examples of peoples which were not from higher caste but despite they were worshipped, for example, Sai baba, sant tukaraam, Naryan Guru, kabir, rahim. We never heard that if fatwas were issued by any higher caste peoples against them. Peoples used to live in harmony and with respect for each other.
Thus we need to stop to abuse this caste system.