Why car manufacturers began opting for curvier designs: The pace at which design changes and the drivers behind it vary wildly by industry, from fashion (seasonal, driven by the whims and fancies of designers) to the automotive industry (the pace is glacial and motivated by external concerns).
In the auto industry, radical changes are generally driven more by considerations such as safety, the economics of manufacturing, and, during the late ‘80s and early ‘90s, fuel efficiency. As Vox explains, rising fuel prices, particularly in Europe, pushed car manufacturers to reduce wind resistance (and thus cut back on fuel consumption) by dropping the boxy shape and sharp angles typical of older car models in exchange for more curvaceous designs (watch, runtime: 4:01).