I do agree that it was very unprofessional for them to be absent in the post fight press conference. Regardless, they know that they have to cover Ryan's back whether he win or lose that fight. Of course, not just Oscar but those who back up Ryan in this big fight is frustrated because we thought that he still has something inside of him to at least give us a good fight. But Davis is just to good, power and has a good defense to protect himself against Ryan's left hook.
This first loss probably affected him mentally but this is also where greatness will happen. You lose one, you get back as a stronger fighter, and you polish the mistakes you had done. I don't think changing trainers is the solution to being a better boxer. This year will be a big challenge for him.
You need to understand everything after your loss, if you want to come back strong you need first to accept your defeat and use it as stepping stone to move forward, there's should be no issue about losing a fight and if this concern about his coach will continue to spread, it will not help his career, if he fight again with a new coach and loss then the reflection will continue be negative.
Better to quietly work with how to improve yourself and, for now, stay away from social media. It will help him to focus and regain his former place.