First of all, you have to realize that people are no different in or out of the congregation. Even though JW's say they're special, they're not at all special, they deal with the same problems, desires and people than the rest of us. People are going to be stupid, do drugs, live hedonistic lifestyles both in the world or as JW's.
Second of all, you're hanging out with the same people you were in the congregation with. Many of them simply rebel against what they have been thought their whole life and think they're invincible. They had the same desires to do this in the congregations but it is suppressed instead of helped resulting in deviants.
Third, many JW's are a bit slow in the head or have other mental issues, they're behavior is not representative for the rest of us with an IQ over 100. Simply count the people in your congregations who were bipolar, take regular mood-altering drugs (painkillers, anti-depressants), are depressed or are just plain crazy. Then also count the people that couldn't or didn't want to complete high school or even an associates degree. I did a rough count today and I came to 50% confirmed cases of diagnosed mental illness (where meds or guidance is recommended by their doctor), 75% of them did not have even 2 years of college and I live in a fairly well-off urban area.