All their bible study books start with the happy stuff and towards the end move on to armageddon. By that time, you already "know enough about Jehovah" and might buy into the idea that you now have enough "accurate knowledge" to be destroyed at Armageddon if you don't repent, start preaching, attend meetings and get baptized.
That routine has worked well for them, but fortunately more people are avoiding that trap with the help of the internet and concerned families who have better information on how to help them stay out of it.
How many people would they get if Chapter 1 was about Armageddon and who wouldn't make it through? Haha!
And, the paragraph/answer format weeds out anyone who wouldn't want to parrot back an answer to them obediently. If you make it to the Armageddon part, by then you are accustomed to parroting and agreeing without question, and you are a good candidate for cult membership.
I'm not sure if it's brainwashing, maybe it is, mostly it's just refusing to think critically. It's laziness combined with a pessimistic world view. They will always get some converts, I think. Even with the internet, but not as easily as before.