The eye-popping $5 billion fine the European Commission levied against Mountain View, California-based Google this week marks one of the first major, global antitrust actions against the search giant.

It’s also raised a slew of questions around why the commission chose to take a much stronger stand against the tech giant than U.S. antitrust authorities have. Some have posited, like President Donald Trump in a recent tweet, that it’s simply a matter of European trade protectionism.