Bayern Munich decision not to extend Tolisso contract is the right thing in my opinion, because Tolisso has often been injured so he has not been able to make a big contribution to Bayern Munich, I don't know the reason for OL decision to sign him again, because even though he is still young but his performance so far every season has continued to decline, especially since Corentin Tolisso injury history will be hampered his later performance with OL.
He has never been fully accepted in the team. In 71 games, he scored only 11 goals and make 7 assists for goals. His injuries have made more difficult. 5 years in Germany and now it's back to his old team Olympique Lyon. He is even a national player and was 2018 Worldchampion 5x German Champion and 1x Champions League Winner, so money they will make with him, he is only 27 years young.
It's true as you said if he is 27 years old and I think he has 3 years left for him to show his best performance in football, because I think if a football player is over the age of 30 it will be difficult to develop well later, especially during this time we know that tolisso is a player who often suffers serious injuries so I think if OL can't expect too much from him, his failure at bayern munchen is not because he is a bad player but his frequent injuries make him fail to develop and OL should pay attention to that before returning bring it home even though for free.