As of today, he has not been more successful than Glenn. Now, if they make it to the Super Bowl, yes. You forget the Lions were in the championship last year.
Glenn isn’t responsible for the team. Glenn can’t be contributed to one of the best offenses in the NFL that allowed the Lions to reach the Super Bowl while never putting up a top 15 defense, just like Brady can’t be blamed for a defense that allows over 30 pts by an offense while making a top 10 offense.