Famous, yes, but there can also be incorrect assumptions in that. Galileo, for example. A lot of people assume his heliocentric model was correct and was only rejected because heliocentrism was considered heretical because it contradicted the ruling assumption of geocentrism. But the Vatican at the time was seriously considering a number of models including some heliocentric models. One of the reasons Galileo's model was rejected, was because it contradicted observations. Planets didn't quite move in the way he predicted, and that's because Galileo clung to the incorrect assumptions that orbits had to be circular.
Of course his core idea of heliocentrism was less wrong than geocentric models, but at the same time it's an example of how addressing one incorrect assumption can lead you into another incorrect assumption. And that also lead to a lot of resistance to your idea, even if the core of your idea is correct.
As for Darwin, a lot of people at the time already assumed that something like evolution had to be going on, and that many animals had common ancestors. They just didn't know how it worked. Even while Darwin was working on his theory, Alfred Russel Wallace was working on the exact same idea. So in that case, the idea was actually obvious to anyone paying attention, and Darwin happened to be the one to get there first. But if he hadn't published about it, Wallace would most likely have done so.