Rangefinder cameras are the most successful camera system recorded the last World War (WW II) with rangefinder cameras from varies manufacturers, most notably Zeiss. Leica was late to the game and its Leica IIIa was regarded as less rugged and lightweight option of the beautiful Zeiss Contax II which was the professional choice of its time.
Zeiss as a company turned 100 years old in 1945, the year World War II ended, the America troops that occupied the Thuringia and took 77 top scientists and engineers with them when they moved into their zone after German division, the Zeiss Oberkochen built and the old Jena factory was nationalized in 1948, East Germany, changed the course of history for cameras.
Leitz has better luck, and after the war, it continued to produce the Leica II and Leica III through the 1950s. Around a decade after World War II, in 1954, Leitz introduced the Leica M3, with the new M mount, established the common perception today that Leica M is the synonym of the rangefinder camera. Without a doubt, Leica deserves all the credit for what they delivered and achieved and they made some of the best-crafted and beautiful cameras and lenses.
With relentless endeavor, Leica entered digital age with competitive offerings adhered to their core tradition, for example, their latest rangefinder cameras, the Leica M10, M10-P, and M10-D.
The rangefinder system camera was a result of camera technology development from the needs of users in the fields, as the reflex system came after, and electronic viewfinder systems now. Some may argue that the new one may not be better than older ones, common, they usually are. However, the new one does not always make the older one useless, in many cases, the older one evolved through time to have particular application and usability the newer ones can't quite replace, such as the rangefinder camera.
The Fujifilm company founded a year after the birth of Leica II, in 1934, became the first Japanese manufacturer for photographic films and entered into camera manufacturing in 1948 with their Fujica Six and in the early 60s started to produce broadcast-quality lens to establish its name in high-end optics and camera making. Fujifilm was the most agile among film makers in adapting to digital imaging with very successful APS-C X cameras and in 2016 Fujifilm re-entered the medium-format market with a digital offering - the GFX system, shortly after the Hasselblad X1D introduction.
Unlike Hasselblad's forward-thinking X1D system, Fujifilm debuted their GFX system with model 50S which reminiscent of old fashion reflex-style medium format camera with a film magazine and quickly learned the market feedback with the following model 50R in so-called rangefinder style and made it available to the market as fast as any camera manufacturer capable of, by December 2018.
So we have two cameras in the picture, the Leica M10 - the true rangefinder camera, and the Fujifilm GFX50R - an electronic-viewfinder mirrorless camera in rangefinder style - which usually referring the viewing window is at the far end of the camera so the camera user could use one eye on the viewfinder and the other eye sort of able to observe what is happening outside of the viewfinder. Of course, the rangefinder also offers a unique viewing experience that the viewfinder actually allows the user to see more than the exposure area, therefore, allowing to capture those "perfect moment" because they see the action ahead of the exposure frame - this is perhaps something hard to replace for the time being - and this is the advantage of rangefinder.
Rangefinder camera also typically more compact but that also limits the range of lenses due to the rangefinding mechanism limitations as the case of Leica M10 camera, the focusing range is 70cm to infinity, lens range from 28mm-135mm (28/90, 50/75 and 35/135) but realistically, only 28-50 really useful if one wants to have the frame composition to be reasonably exact. Or, use an external EVF which works but left much to be desired because of Visoflex Typ 020 not only partially cover the shutter speed dial, it has relatively weak resolution for today's standard and it is slow, and horrible to use in rapid succession of shooting. But that somehow opens up something for M system, for example, macro photography and adapting some legacy Leica-R lenses or other alternatives.
In reality, most types of photography and photographers do not benefit from using rangefinder camera. But why Fujifilm intends to market the model 50R as "rangefinder style" while it is nothing in common with Leica M except it does look somewhat similar in appearance, yet it is so much bigger.
It is possible that Fujifilm would like to have the design of the GFX system camera with a similar look of their successful X line and also the model 50S is really too bulky, and looked out of date, even though it does offer good handling. But "style" has more weight in current time than in the past, and 50R is indeed smaller and easier to pack for travel, even at the cost of compromising handling.
Another reason could have been that Fujifilm wanted the GFX system to gain more traction so to make it in different look and market at a more aggressive price will help reach the mass and rangefinder style seemed a safe move. And it appears the model 50R did not fail them.
The representative of classical rangefinder camera in 2018/2019 - the Leica M10/M10-P with mid-range-priced 35mm Summicron will cost 68% higher than the bundled price of Fujifilm GFX50R with GF 45/2.8 R WR lens which has the similar focal length in equivalence, yet the Fujifilm GFX sensor is 33X44mm - about 68% bigger than M10's 24X36mm sensor, with more than twice the resolution (51mp vs 24mp), and a bunch of other functions, including 1080P video and Fujifilm's film-simulation modes ( many like it and I have never used it once and not intend to use it). Based on all measurements, the Fujifilm is the choice of the two for the one who looks for the higher potential of image quality and in my opinion, it is. But man does not make the decision purely based on measurement, many value emotion over measurement or sense of logic, and Leica as a much smaller company compares to Fujifilm got their own success in the market.
Indeed, not everyone needs the higher resolution camera and not everyone can get the better picture from higher resolution camera because the final quality of an image is the combination of many factors, from the photographer, from the situation, and from the camera. And of course, not everyone needs the largest possible prints and Leica M10 is already quite capable of producing image quality sufficient for very large prints that can meet most needs.
And today, the Leica M10 sits on the low-end of sensor resolution and camera functions of the full-frame digital cameras and Fujifilm GFX50R, although in-expensive, sits among the top along with GFX50S and Hasselblad X1D as the higher-end of sensor resolution and camera functions for 33X44mm format (by the size of 120/220 roll film - the 56mm is what used to define the medium format) yet the M10 costs a lot more which says in 2018/2019 - personality and style is the key!
In fact, it always is.