I believe that teams that won the championship of their league get an extra boost in fan enthusiasm at the start of the season, that decays away as the season progresses. This was designed to give teams that promoted some time to adapt to their new league, kinda like the fans were so excited to see them play in a new league that they were a little more pumped. I didn't implement this feature, but it might be that it was added to all champions of the previous season and not those who promote... i will ask charles but it would lead to this effect.