Could be a lot things, without more detail it is hard to say. But level is only one of many factors that determine how good a squad is. Other ones being:
I would say don't look at the level of the toons or the GP, look at the actual toons and the composition of the squads. A lot of teams can counter teams that have a much higher GP because of the kits they have!
Focus of which teams counter others and try to build your gear as high as you can
Replies
Gear Level
Ability Level
Mods
Squad composition
matchups
Focus of which teams counter others and try to build your gear as high as you can