Rule of an easy life in game, is to always look for an IF when you travel if you have bounties especially. They are always in Low Security systems, eaoe if that helps, and the system map will tell you this.
I think what happened in your case - you had been there before with a dormant bounty and you were lucky that the fuzz didn't scan you. But this time they did, and the lure of 200cr put you on their radar, despite the multimillion credit pirates whizzing about too! It may sound silly, but they don't differentiate by value, anyone is criminal when they have a bounty.
Ps - fines used to evolve into bounties after 7 days, but I think they removed this, as it caused a lot of tears...!
