Recent rumors state that Fuji and Kodak will join the Micro Four Thirds march. This is quite interesting since the original Four Thirds system was an open standard, but the only companies that showed real appreciation were the two leaders, Olympus and Panasnonic. The Micro Four Thirds is on the other hand, a closed standard but it seems several companies are knocking on the door. Being rational, the mirrorless (live view) system is very attractive, but is also new that supplying lenses for different purposes is a problem in hand. This problem could be overcome with less effort in haste if more companies share the lense mount and that must be the main reason that minor(?) consumer camera brands (such as Fuji and Kodak) want to cooperate with the Micro Four Thirds system. This rational side of view against the situation is what most people can see. Now, let's have a look on the silly side.
So the silly answer that I came up with is that the name Micro Four Thirds is the magic for popularity. The abbreviation for Micro Four Thirds is "M4/3" and what is the big deal about "M4/3"? Well, its got "M" inside the name and all lense mounts with the letter "M" were popular. Let's start off with the M39 and M42 lense mounts. The old M39, also known as the "Leica Thread Mount" or "L Mount" was so popular that most of the old RF lenses we see today are for the M39 mount. For the SLRs, we have the M42 mount, originally by the East Germen Contax, but more known as the "Pentax Thread Mount". Made by Contax, popularized by Pentax and other East European companies, type in M42 in Ebay and you'll be flooded with results. Both the M39 and M42 mount did fade out as the bayonet mounts started to show up, but both thread mounts were wide used as the standard of RF and SLR systems.
The bayonet lense mount age also became the golden age for the SLR system. Almost all SLR camera brands had their own mount, but none of them (as far as I know of) used the world "M" for their lense mount and surely no one mount dominated the market. [Canon: Fd and EF] [Kyocera's Contax and Yashica: C/Y or Y/C] [Leica: R] [Minolta: SR and Alpha] [Nikon: F] [Olympus: OM] [Pentax: K] There should be a few that I missed out, but anyway, I don't believe any of them started with the word "M" in their lense mount names. In the case of RF, however, Leica seemed to be the only manufacturer that survived from the SLR rush with their M mount. This M mount became the standard for the RF system and companies like Minolta and Rollei also introduced lenses and cameras for the Leica M mount. (Let's skip the story of Leica and Minolta's collaboration for now, please. Remember, I'm only trying to be silly here.) Later in the years, companies like Cosina (VM for the Voigtlander brand and ZM for the Zeiss Ikon brand) and Konica (KM) came up with their own "M" mounts, which are 99.9% compatible with the Leica M mount, proving(?) that the M mount is the standard of RF lense mount.
Great work for Olympus and Panasonic for calling naming their mirrorless system, the Micro Four Thirds system, instead of Hybrid Four Thirds or Live View Four Thirds or New Four Thirds or Four Thirds 2 or...