Some Reasons Why Ahaadeeth Were Fabricated in the Past
Some of the reasons why ahaadeeth were fabricated in the past are:
1 - Political reasons (e.g. Shia, Ummayads, Khawaarij, etc.)
2 - To hurt Islam (e.g. munafiqun, etc.)
3 - Nationalistic reasons (e.g. those fabricating ahaadeeth praising their homeland, heritage, etc.)
4 - Storytelling and preaching (i.e. there were storytellers who only cared about grabbing people's attention and gathering them together in sessions to pay attention to them and spiritually inspire them regardless of whatever ahaadeeth they had to fabricate in order to meet this goal)
5 - To earn a living (e.g. people would earn money by getting people together to listen to them narrating ahaadeeth which they would fabricate)
6 - For the good intention of increasing people's faith (e.g. some saints and pious people would fabricate ahaadeeth which motivated Muslims to become better worshipers of Allah)
7 - Championing ones own madhab (e.g. some adherents to madhabs would fabricate ahaadeeth in order to support juristic opinions espoused by their madhabs)
8 - To please the rulers