The EU by going after the self-mixing market. Bullshit like allowing duties on liquid that doesn't even contain nicotine so you end up paying through your nose for flavoured glycerine/propylene glycol mix. Limiting nicotine-containing liquids to 20mg/ml max, and 10ml bottles at that, while there were never any issues with what was legal here (Germany) under ordinary toxic substance laws (without being a chemist): 50mg/ml in any size you bloody want (usually 100ml because it degrades once you open it).

Before those laws the market was largely modular systems, tank and mod separate, plenty of replaceable batteries, with all that bullshit added on vaping sensibly became so expensive that people went "meh, can just as well use a pre-built".

The UK actually were the sensible ones in that area, but I guess the market shift reached them by sheer force of Chinese production capacity.