The reason? Over its Android operating system and possibly a case of abuse. This is mainly due to the fact that Google bundles its own software and services with Android, such as Google Search, Gmail, Maps, and so on. The main issue here is whether or not Google’s bundling of their own products might have prevented the competition from gaining any leverage in Android.
In some ways this is similar to the issue Microsoft faced many years ago with the bundling of Internet Explorer with Windows. That being said, the inquiry by the FTC is said to be in its early stages and for all we know, it could end up being nothing as they might not necessarily find that Google has abused its dominance, but either way it’s something Google needs to deal with.
This isn’t the first time Google has been accused of abuse. Last year a lawsuit was launched against Google and just last month, Google dismissed any antitrust concerns against themselves over in Europe.