Pentax and Leica went into Full Frame Digital Cameras.
Their market share is much smaller than OM and Panasonic.
Fujifilm etc went into Medium Format
Again their market share is much smaller than OM & Panasonic.
Points to note:
1) Larger sensor size does not mean higher market share
2) Going into Full Frame does not guarantee any manufacturer market size or success
3) Having smaller market share than Full Frame does not mean they will die off.
Pentax, Leica, Fujifilm Medium Format are still surviving even though they have a smaller market share than Olympus.
You don't need a huge market share to survive, it is all about management, marketing and planning.
Small market have their niches too.
Don't buy a camera based on its popularity.
Buy one that meet your needs.
For example, a group of us was at the Rugged Coast on St John's Island to shoot Corals.
The Corals are less than knee deep, so we do not need to go underwater and you can bring along a
popular brand mirrorless if you choose popularity over practicality.
Almost all of us have a mirrorless slr, but none of us brought. 4 out of 8 of us
brought our Insta360 cameras instead. Insta360 actually have a 50% market share
yesterday evening! Simply because it meet our needs better.
p.s. The Insta360 sensor is less than M43 and 1 in.
I really like the film Olympus OM-1 designed by Maitani.
I have a few film Olympus OM-1 camera bodies.
Which I keep out of respect for the designer.
I do not like the current crop of digital OM Systems mirrorless ILC.
In 1973 when Maitani designed OM-1, he was not small minded about the format.
Actually by that time Olympus had already made its name making half frame cameras.
Maitani designed OM-1 to be Full Frame 35mm. i.e. 24 x 36.
Maintani knew that if Olympus wanted to compete with the big names Canon/Nikon.
He knew that he cannot be small-minded about the format.
Unfortunately his successors in Olympus were far below his quality as a designer.
Thus in 2008 they chose the MFT format.
Which in 2008 seemed great.
But in reality this was just like the proverbial dwarf DNA cast in stone in the MFT design.
It can grow for a while in popularity and world wide sales initially after 2008.
Bu thereafter like a dwarf, it stops growing.
Other brands with Full Frame surpassed it and left Olympus in the dust and to die in the rubbish heap.