According to ESPN, Ehlinger has been turning heads in the Colts’ locker room for some time, but even so, he has yet to throw a pass during a regular season game.
Ultimately, though, Ryan was benched because the Colts have proven to be one of the worst offenses in the league through seven weeks. They benched him now because, with their record of 3-3-1, they can still make a run for the playoffs. To do that, though, their offense will need to start performing much better.
Source: https://www.distractify.com/p/why-was-matt-ryan-benched