This has been pushed by the Enlightenment and even before because that's the fairest and most just. For example, the French Declaration of the Rights of Man and the Citizen of 1789:
"All the citizens, being equal in its (the law) eyes, are equally admissible to all public dignities, places, and employments, according to their capacity and without distinction other than that of their virtues and of their talents." (Article 6)
That's what meritocracy means. In the same way as in a fair competition you want the best player(s) to win, not those who know or pay the referee. It does not mean leaving the poorer and less able fend for themselves on the thinking that perhaps it's their fault if they poor.