Lean and lack of muscle. These guys just don't fit the male athlete image.
Jockeys and body builders do the same thing. Most body builders lean right out for competition then go into severe dehydration to get paper thin skin. Jockeys are constantly in the sweat box and always on diets. Cyclists may be lean but they are a lot healthier or they could not generate the power the sport requires. They still eat a lot. Their muscle density is like rock but they have very little fat in their skin.
I know at least 2 locals for 15 years that have never looked like they have any body fat. Summer or winter and you can see the muscle fibre through their skin. One works as a plumber/pipe fitter so he has a little upper body muscle but the other guy is a planner and he looks like a stick. They are cat 1 fast. not pro fast but fast guys.
I don't believe any of these guys are skinnier now than guys 20 years ago but they look a lot taller across the board. Tall and skinny just looks worse than short and skinny.
Add to the fact that we are getting so used to seeing fat people as normal our perspectives are shifting too.
If these guys were sick they would be slow too.
Sorry, maybe I have spent too much time watching them live I don't see the problem. This is what a cycling elite athlete can look like. No reason for strong upper bodies so they have small lean muscles and very low fat. Anorexics don't have the muscle either. These guys have very impressive leg muscles.