They just fell apart. The plastic body meant no rust (I think the roof was steel though)!
Seriously, everything inside just started falling apart after 10 years. Dash, seat belt winders, door panels fell off, radio buttons just caved in, etc. and ours lived a fairly pampered life.
I spent a good deal of my childhood in one. The 3.1L V6 was a dog and the 3 speed transmission meant kicking down was an event and the mileage was terrible. Dad always wished he held out for the 3.8L and 4 speed in '92.