A huge fine for Google, what is the reason?

The Court of Justice of the European Union upheld the European Commission’s decision in 2018 to fine Google more than $4 billion.
According to the court’s decision, the decision imposed by the European Commission previously to fine Google is correct, on the accusation that the company imposed illegal restrictions on manufacturers of Android mobile devices and mobile operators in order to strengthen the dominance of its search engine, and the fine amounted to 4.1 billion euros.