I took liberty to peek in the game code, and i'd guess this issue is caused by the huge impact of your current fame level on the number of new fans you acquire:
private float GetFameNewFansBaseCoeff()
{
return resources.GetFameLevel() switch
{
0 => 2f,
1 => 1.5f,
2 => 0.5f,
3 => 0.3f,
4 => 0.25f,
5 => 0.25f,
6 => 0.15f,
7 => 0.1f,
8 => 0.05f,
9 => 0.03f,
10 => 0.01f,
_ => 0.1f,
};
}
The catch is, fame levels are very easy/fast to acquire. In my game i have fame level 10 after a year or so, mainly from doing contract work. This means my new fan gains are reduced to 1% of what they'd be otherwise, even though i have just a bit above 100k fans total and obviously plenty of room to grow in this department.
As a fix i'd suggest increasing numbers needed to acquire fame (a bump as large as 10x wouldn't be out of place, considering you can hit the max in just a year) and/or improve the fame coefficient calculation to take into account the size of your existing fan base, and don't reduce it so drastically if the players fan base is still somewhat small.
Hope this helps?