then they have been preaching their message primarily within lands that are predominantly Christian based..
Yes. But JW's are present with branch offices in the most populous Muslim country in the world (Indonesia) and the most populous Hindu country in the world (India). I should say JW's were present in countries like China, North Korea, Afganistan till the time they are persecuted. When persecuted JW's are not obligated by Jesus to remain in that country since Jesus said in Matthew 10:23: When you are persecuted in one place, flee to another."
as their are many populous non Christian nations nations that do not allow, even forbid any proselytizing in their lands.
There are 2 lines of reasoning given for these countries which don't have much witnessing work going on:
1. Not all territories will be preached before the end.
*** w97 8/15 p. 14 par. 11 Living for Today or for an Eternal Future?***
True, untouched territories still exist, and perhaps in Jehovah’s due time, a door of opportunity will open. (1 Corinthians 16:9) Still, Jesus’ words recorded at Matthew 10:23 are sobering: “You will by no means complete the circuit of the cities of Israel until the Son of man arrives.” While the good news will surely be announced throughout the earth, we will not in person reach all parts of the earth with the Kingdom message before Jesus “arrives” as Executioner.
2. Countries that don't allow preaching activity bear community responsibility for their actions - the way Egyptians suffered the 10 plagues because of Pharoah's hard-heartedness.
No one would be able to say "They told me about and explained to me the Good news of the Kingdom" and what it would mean to me.
Jw's have been conditioned to reason that they are not responsible for how people react to their message. They need to get going with the work no matter what people say about them. 2 Thess 1:8 is a favorite scripture that says Jesus will take vengeance on those who do not obey the good news. So if people don't remember the good news then it's the people's mistake. Same as if you forget your medicines then it is your mistake, not the doctors.