Are you suggesting that God gave the commandments, known as the Law of Moses together with the natural ability to obey, but then acted only on some, in fact few in percentage, to give them the moral desire to obey? Clearly that same question can be asked concerning believing in God. Are you suggesting that God has made believing in Him, i.e., having faith in God, the critical factor for salvation, but then gives that ability to believe in Him to only some and not others?
What sort of God would do that? Why would God do that?
My answer to such questions is that God would not do such things. He would not act like that. God would not do that and He doesn't do that.