I don't understand how an entity can force Google to change their algorithms. They are a private company and with their own hard work they managed to get as man

I don't understand how an entity can force Google to change their algorithms. They are a private company and with their own hard work they managed to get as many clients as they currently have. So because so many people are using Google as a search engine, they are now supposed to promote competitors of their services because "so many people are using it"? It's like saying "so many people are driving BMW, it's not fair for Audi, BMW should include an Audi advertisement now and then. If they don't, they will have to pay us a big fine!". Isn't Europe a free market?