@Barzda
They are probably very early starting managers and always with same team and working a lot with their popularity all time. Your team had several jumpers as owners, each leaving decreases club's popularity remarkably (25%?) and you can't be sure that your team owners all worked hard to maximize popularity. For example I am little bit lazy and my friend who started about year later has passed me already by popularity.
Those teams had bigger stadiums longer time, chances to get more fans and increase popularity. When I worked more with popularity I also noticed that some top teams which played continental matches and had bigger stadiums had still bigger increase of popularity than I when I sold always all tickets to new users.