The same principle evoked in the rest of this thread, if the penalties match exactly or are under the profits you can generate by injuring (in the legal sense) EU citizens it's not really a penalty but rather a cost of business. Plus markets are very interconnected, especially the digital ones.

EU competition law is not framed around valuing Europeans more than others, it is framed around protecting competition and market functioning inside the EU.

No need to moralize it and pretend anyone is using this "value" European humans more than other humans.

Because they decided that way. Any other country in the world can decide the same thing but they don't have the same leverage as the EU. Google makes a lot of money in the EU.

Why a year, when they've often been breaking the rules for much longer than that?

Why not 20% (30%), given that's the share of world GDP (PPP) due to the EU?

Why revenue rather than profit?

The answer is: big round number that's roughly justifiable as a big stick for, and I want to emphasise this, a punishment to make sure they don't break the rules.

The damages done that caused the fine are usually spread over multiple years.

India is doing 10% as well.

The reasoning is very simple just "carry a big stick", multinational companies need to fear the fines to want compliance.