The internet and some really shitty people that I worked with a while back saved me.
Here's a bit of backstory.
I believed 100% that I would never get old or die because Armageddon would come before then, the Earth would be restored to a paradise and sickness / death would be wiped out for good. I started preaching from door to door at age 5 and was baptized at age 11. My parents have been in since 8 years old, and their parents have been in since their late 20s. Most of my family is in the religion and all of my friends were in it.
I believed in demons and angels.
I believed (as all true Witnesses do) that there were angels watching over us when we were preaching. In the 90s when I was 14 I would preach on a street that had the highest murder rate in Joliet. It was called the hill and was lined with crack houses and gangs on the corners. Also I'm white and everyone that lived on the hill was black. I preached without fear because I knew that I couldn't get murdered because god would save me with his angels.
Demons were very real as well – every Witness knows a few stories or has a friend of a friend that had a demon possessed item. I had reoccurring nightmares from the time I was a child onward that I was being attacked by demons, or that a family member was actually a demon waiting to kill me. I was genuinely afraid of the dark and especially mirrors in the dark until I was 28 years old.
I had never been exposed to other religious teachings or education surrounding evolution or cosmology. Instead I learned about these things from the Watchtower's publications which are of course slanted against science in their own special way.
the people I worked with were atheists and had no idea I was in a (mostly) fundamentalist religion until I had been hired. They launched a series of attacks on my beliefs, looked up videos and stories on the internet about Witnesses (after I told them I wasn't allowed to) and essentially forced those things on me.
In truth, this just strengthened my faith... but then something changed. They started acting friendly to me instead of attacking me on a daily basis (I think that's because after 2 years I had enough and threatened to sue in an email). Down the line this gave me the chance to ask them if they had ever seen demons (I knew they all did drugs and I was always told this is a way for demons to take hold of your mind).
They of course laughed at this question and assured me that they had never seen a demon. I then asked a good friend of mine from that job who had grown up doing drugs and around drugs if he had seen demons. He hadn't either. This got me curious so I started researching demons on the internet and found that they're basically treated as mythology.
That pretty much opened the floodgates. I researched homeopathy (I didn't have a real doctor until my teens – only a homeopathic chiropractor) and found out that it was pseudoscience. When I brought that up to my mother, she had a reaction that was similar to attacking someone's faith – that bothered me greatly and I realized in that moment that she was willing to believe everything. From there the entire house of cards fell, though very slowly. It took about 2.5 years to fully break free from the beliefs I once held as true and the internet is ultimately responsible for keeping me out. I was able to use it to research forbidden knowledge and join communities of other ex-witnesses who were struggling with the same issues.
Now I'm an atheist. My family relationships are strained at best (I've seen my parents and sister one time in the last 4 years, though they will speak to me briefly on occasion). I lost all of the friends I had built up over the years and as of last year I was totally alone save for the one good friend mentioned above and his girlfriend. They helped me to get through this by letting me hang out at their house a lot.
These days I'm doing much better. I'm so much happier without religion. It vacuumed up every iota of my spare time and I received nothing in return. I am convinced that all religion is destructive and corrupt, including Eastern religions. I think the notion of a god and spirits is laughable to the point of embarrassment and to deny science is to deny your own existence.
You are correct that most born-in Witnesses would never leave. That's because it means completely upheaving your life and becoming someone new. For many people that means drugs, sex, alcohol and partying – the things they weren't allowed in the religion. I did these things myself, but I was able to slow down and catch myself before I hit the bottom. Others hit bottom and stay there, or come crawling back to the "loving" arms of the organization.