Medium format SLRs for non-specialised use are a totally different breed than 35mm cameras. The current shape of the 35mm SLRs were defined between the 1930s and the early ‘50s, and the most critically influential design is, without the shadow of a doubt, the Kine Exakta. What we identify as an SLR today is, almost without exception, a scion of the Exakta. The other is the Contax S, which ported the concept of the Kine Exakta into the Contax rangefinder body, which was inherently superior, plus, they added the pentaprism, without which most of us don’t understand an SLR. For medium format cameras, designers followed different strategies.
The main influencer in medium format SLR design is the Hassy. The original Hasselblad is allegedly based on a German aerial camera. Should we trust their founding myth, and you know what do I think about founding myths, it is a military tool adapted for everyday use, which is creepy enough.