Indeed, as a manager only have one job, namely to improve a team so that they can work together well. However, when the club's condition is experiencing a drastic decline, of course it is a difficult task for the coach, while Diego Alonso was just brought in by Sevilla last October, which means Diego Alonso has just been at this club and as a coach of course he has to adapt first so he can build good chemistry and be able to establish good cooperation.
I don't really understand whether Diego Alonso is the right coach for Sevilla if the coach is immediately dismissed because we don't really understand the strategy that the coach has. I think Sevilla should be patient for a while until they really prove that Diego Alonso is not a coach. which are suitable.
However, yes, I understand why Sevilla did this because they don't want to experience continuous decline, they just move quickly to improve the team's performance quickly because their position is already threatened with being close to the relegation zone and if in the end they make the decision to fire the manager, hopefully this is a good decision the best they took.
Every managers dream is to be successful with his team and meet up the target given to him by the club's board members as well as impressing the fans to gain their support buy it goes the other way round when he lacks the right strategy to handle his team and get them to do better, a team like Sevilla with a good history in the Europa League and Laliga shouldn't be struggling to win matches, well it's understanding for the Sevilla Board members action in sacking Diego Alonso, cause 9weeks was enough for him to get the team in doing better like he was signed for.
And since he wasn't getting things right after 9weeks as their manager, they could take chances and watch their club go down the drain, therefore they needed to take drastic actions before things get worst for them this season, anyways let's wait and see their next choice for the managerial role and if he'll be able to do better than the previous season.