Certainly, taking a nontrivial percentage of global revenue will force Google's attention, but I'm not convinced that's the best way to think about it.
One thought: if Google had just served non-personalized ads (or personalized ads with much greater restrictions) to all of France, how much money would they have lost due to the ads being lower quality? With some very rough estimates, I'd guess $250 million in revenue resulting in $100 million in profit. ($1 billion revenue from France, $500 million from ads, ads are 2x more effective when personalized, 40% of revenue is profit). All very rough estimates/analysis, but it definitely seems like a significant slice (half the profit) of this part of Google's operations, and likely there's at least someone at Google who's thinking about this specific revenue source who just got a wake-up call. Given the roughness of the estimates, seems possibly at a point where it would have been better for Google to just give up on ad personalization (at least in France) altogether.
Another thought experiment: surely at some point (e.g. fining 100% or more of global revenue), Google will just stop operations in France (or Europe), which is probably not what anyone wants. What is that tipping point? If every country (or city) uses the "significant percentage of global revenue" approach, it's more likely to collectively become unreasonable. That's at least the extreme-case downside to giving a fine that's too big (especially proportional to the unfairly-gained profit in the jurisdiction giving out the fine).
I guess it's a complex decision, but I feel like if I was running a worldwide business and a single country decided to impose a $100 billion fine (the scenario I was describing), I'd want nothing to do with that country. That's much, much more than the market opportunity that Google has in France. Probably I'd want to avoid operating at all in countries that have a chance of imposing that scale of fine.
This is not a single country -- as the article mentions, this decision is valid for the entire EU. Obviously, there will still be some kind of limit for individual businesses, but a 50M€ fine is nowhere near enough for a company like Google to stop doing business in the entire European Union.
One thought: if Google had just served non-personalized ads (or personalized ads with much greater restrictions) to all of France, how much money would they have lost due to the ads being lower quality? With some very rough estimates, I'd guess $250 million in revenue resulting in $100 million in profit. ($1 billion revenue from France, $500 million from ads, ads are 2x more effective when personalized, 40% of revenue is profit). All very rough estimates/analysis, but it definitely seems like a significant slice (half the profit) of this part of Google's operations, and likely there's at least someone at Google who's thinking about this specific revenue source who just got a wake-up call. Given the roughness of the estimates, seems possibly at a point where it would have been better for Google to just give up on ad personalization (at least in France) altogether.
Another thought experiment: surely at some point (e.g. fining 100% or more of global revenue), Google will just stop operations in France (or Europe), which is probably not what anyone wants. What is that tipping point? If every country (or city) uses the "significant percentage of global revenue" approach, it's more likely to collectively become unreasonable. That's at least the extreme-case downside to giving a fine that's too big (especially proportional to the unfairly-gained profit in the jurisdiction giving out the fine).