The decision to keep the Google owned platform Youtube, on their newer devices comes with a multiyear distribution deal between the two companies. The decision to keep the app on the Roku platform comes just a day before Googles deadline to keep Youtube or cut off the main Youtube app. This agreement with Google and Roku also allowed Youtube to be restored to Rokus channel platform just a few hours after the decision was finalized on Wednesday afternoon. Youtube is known for being the world’s largest platform of digital videos with a total number of more than 2 billion monthly visitors to the site. The decision to allow the app back onto Roku streaming services will allow many to enjoy and watch Youtube all while still staying on the Roku platform. The Roku platform is also well aware of the fact that even though Google owns one of their largest used apps, Google is still a huge competitor in the field of streaming TV with some of the others being Android TV, and Apple TV.

Sources: 

https://www.cnet.com/tech/services-and-software/roku-google-strike-deal-to-keep-youtube-running-restore-youtube-tv-on-rokus/