Exactly, if Alonso wants him to be continuously praised as a good coach, he needs to repeat the same thing he did in his first season at Bayern Leverkusen coaching them. At worst he should not be on the wrong side of the final result after the season. He is a respected coach more since he won the trophy without losing any match. He needs to continue that performance with them until he fully believe and make that impression to everyone that he can be the best coach everyone wants him to be and like other successful coaches and not just a lucky one as others might foresee it.
I'm not really sure that next season Alonso will be able to repeat his success like now because if you look at it, several other teams will definitely try to improve their strengths. But if Leverkusen buys some of the players needed at least he can maintain his position in the top three of the standings. Alonso hasn't really been tested because he has only given good results for the team for one season and I think he needs real proof for him to become a coach who will be taken into account in the long term.
Defending is much more difficult because they are not supported by players who have the capacity like Bayern Munich in the previous season. So Alonso's steps will be a little more difficult to defend the title because the abilities of the players he has have not been tested like the Bayern Munich players in the previous season.