Flick led Barca to the LaLiga title last season and has the team currently top of the table.
Deco said "When Xavi decided to leave and then stay, and then that whole episode unfolded, we understood that we needed a coach capable of bringing some calm to the dressing room, especially regarding the age differences.
"We've always had a very unique dressing room. It's becoming more balanced now, but we still have very young players, others at their peak, and more mature players like Raphinha, Frenkie (De Jong), and Jules (Kounde).
"There's also Robert (Lewandowski), and, for example, (Marc-Andre) Ter Stegen, who's currently on loan but is one of the captains. Over 30, we have Robert, Marc, and I think (Wojciech) Szczesny as well. Managing a dressing room like that is very important.
"That's why we believe the key was to have an experienced coach, and in this case, one with extensive experience managing important dressing rooms."