But again, why just in Judea did god choose to send his son? 99% of world had no idea it happend at time. Why would not god appear to the aztecs/chinese/hindus himself, instead of letting them wallow in their paganism for millenia, only to be introduced to the Truth by colonists/ explorers who often did not have the best of intentions at all?
We do not know the answer to this. We do not know why God chose the people of Israel, and out of them at some point was born the Incarnate Word in which all the nations of the world can find salvation.
We just humbly know that this is how things are

We have consistently known for 20 centuries, and while the members of the Church are not impeccable, the Church and Christianity have shaped the world we live in for better. I believe you don’t quite realize just how bad things were even in the most civilized cultures, and how even the most basic things that we take for granted were the fruit of Christianity and almost entirely absent in the world.
Certainly we are not claiming that everyone else was evil. God inscribed His law upon all human hearts. We see His goodness present in every place and time. But Christ was God who walked among us to show us how He was and what He wanted. From that day on, nobody can righteously speak of a God being unfair, or punishing, or not caring, for Christ embodies all the attributes of God. The teaching He brought forth changed the world, because for the first time we were taught to see God in the sick, in the weak, in those who suffered, who were persecuted. We were taught that whatever we do to the least person, we are doing it to God Himself. We were taught that even the dead would hear His message, and those who listened would live. As for us, we were taught that if we did His will, we would never die, but live eternally and attain in the fullness of time the resurrection of the glorified body. As for His will, He said it clearly: “love one another, do unto others as you want them to do to you, do not judge others, love your enemies, pray for those who persecute you, seek the Kingdom of God first and all will be given to you, ask and you will receive and your joy will be made full.”
This is what a Son of Man born in a small town two thousand years ago and a handful of humble workers brought to the world, despite horrible persecution. Not just colonists, but many missionaries all over the world, many of whom traveled in unexplored territories amidst hostile cultures that did not mind killing strangers. And we still have many missionaries today all over the world, who renounce everything and travel to the harshest lands in the world to share the people’s poverty and bring them hope and the Good News of Christ. Just consider a few examples: Franciscan missions in
Central America and
many other places,
Missionaries of Charity,
Passionist Missionaries,
Catholic World Mission…many every year die, such as
these three Xaverian missionaries in Burundi…a “short” list from 1700 to 2011
here… Perhaps you do not know that Christians are the most heavily persecuted religious group in the world, with over 100,000 martyrs every year who are murdered simply because of their faith in this God of mercy who said: “I did not come to seek the righteous, but sinners to repentance…I did not come to condemn the world, but so that the world could be saved through me…all judgment is given to me, but I judge no one…remain in my love.”