The old Challenge Publication "Military Modeller" was featuring a lot of this by the late 70's. IMHO, much of this was overdone but it was the only mainstream magazine many of us had. I think what happened next is that a lot of people used that as a reference and tried to replicate this, then a next generation tried to emulate them and the cult of overweathering took on a life of its own, so much so that the RRB often contains the comment "add more mud." Again, IMHO, some weathering is good. Less is a lot better. Whllie we can find pictures of mudbogged vehicles, there are more of dusty rather than mud soaked that show up.
Anyway, that's my take on it.