Originally Posted by Jeff Wills

Yeah, this went toward “mountain bike” when the OP mentioned gravel riding,
The thing is, in that era bicycle design was really divergent: either a “mountain bike” for off-road or a “road bike” for not. The latter often had very minimal tire clearance, many times you couldn’t fit larger than a 25mm wide tire under the fork crown.
The space between these two designs was so great that the “hybrid” bikes started to appear around 1990. These had space for 35 to 38mm wide tires, flat handlebars, stable geometry, 700C wheels, and mountain-bike-ish components. Look at the Trek Multi-Track bikes for examples.