Fan bug ? From 100k+ to 2k

I had more than 100k fan in my game and a few moment I just saw that I had only 2k fans. I didn’t have any negative event on fans and I don’t know why the fans disappeared.
Is this a bug or I don’t get something ? Anyway, useless save now and I don’t want to make a new one from the beggning.

At what point of the game did issue occur? By the way, it only takes around 2 hours to get to year 35, if this issue doesn’t go away, then starting a new game wouldn’t be that bad.