It's been explained before but Thiago Silva is the de facto captain of the team. The armband doesn't really mean much in that sense, because the leaders will always still lead. If you had taken the armband off Kompany and given it to Sterling for example, Kompany would still be the de factor leader of the team. Enzo, as young as he is, is a leader. Chilwell, whatever one thinks of his quality as a player, is one of the leaders. So is Reece James but obviously he can't stay fit.
Poch literally said about naming Gallagher captain that between him and Enzo he picked Gallagher because he speaks English and can speak to refs, which tells me Enzo is actually the one he wanted to pick but his language skills isn't there yet to be the official captain.