GDPR - the core of it - is about privacy, it's an increment on prior laws in EU countries. It's also in part a response to the data hungry US tech companies, without question.

The 4% of worldwide revenue fine potential is exclusively targeted at the US tech giants. By my last count, the US has roughly 100 tech companies worth over $10 billion each (with trillions of dollars in worldwide revenue). Nobody taxes revenue, that's about the most moronic thing you can possibly do - unless you're doing it to try to harm / punish companies. Very few EU tech companies have meaningful worldwide revenue to tax.