I've been involved with e-cigarettes since around 2011. Quit a 2-1/2 pack a day habit after 50-years of smoking in just a day or two, but had to order all my parts and liquids out of California. There was almost no vape shops in the US at all back then, just mostly mail order stuff and much of it was not easy to use (basic "510" atomizers). Over the years, I helped probably 200-300 people quit cigarettes, mostly using the simple "eGo" e-cigs.
Amazingly, most grown-ups I helped would instinctively reduce their nicotine content in their liquids after a few weeks and then after a year or two, many would either stop vaping or start using a zero or very low-nicotine liquid - just for pleasure. At that point (say, 2012-2014), with proper assistance e-cigs did the job well, was safe and didn't annoy other people, and was relatively inexpensive.
Then a few years back, China let loose the dogs and started producing high-wattage fog machines instead of just simple units to help stop smoking. People started having batteries explode. I was driving behind a guy with a high-wattage e-cig last year and thought his car was on fire. Now, many restaurants are banning e-cigs for that very reason, as they scare the shit out of people seeing the vape fog in a closed space. People with no damn common sense ruin anything that's good - sooner or later.
China started producing hundreds of various fancy battery boxes (called mods) with elaborate electronics, and the e-liquid tanks are now mostly high-wattage. Therefore, I've seen the industry transformed from something purely to quit smoking into a multi-billion dollar industry that mostly promotes e-cig use as a show-your-ass fad, much like the "who got the biggest gun" fad.
I knew a while back there would be blow-back due to the kids and it's no surprise the FDA came down hard......