They are going to introduce a flat fee for every install of a game. From what I know, they are promising to not count Game Pass and charities (and we already see how this promise is being upheld) and pirated copies (how this will be tracked though?), but they are going to charge for multiple installs of a game by one user (reinstalling or changing phones, for example).

In certain conditions, this fee can be more than 100% of the game's gross revenue.

This video explores the probable reason