Because the european single market has a GDP of about 16.3 TRILLION dollars (2020 estimate, source; https://en.wikipedia.org/wiki/European_single_market)

By GDP, it's the third biggest market in the world, directly behind the US and China.

Microsoft and Google are not shoestring budget bootstrapped startups - they can afford to run multiple products, or multiple variants of the same product adjusted for market need, and they will do it, as long as it's net profitable for them. Sure, it's nicer to earn X than X/2 or X/10, but as long as it's a positive amount, it's still worth doing.

That is, as long as it's more profitable to do it by the books than what a lot of industry players did so far, which is to spend money on malicious compliance and sabotaging GDPR.