The 135mm focal length was once the preferred lens for a telephoto lens; not too long, often hand hold able and compact.
Why did it become an almost rejected lens?
I am currently looking for an affordable 135mm that has been sadly missed in my lens line up.
Why do you believe it is an "almost rejected" focal length?
I can only speak about my own gear, which only consists of older items made 30+ years ago. I do not know what other manufacturer currently offer, but Leica's current product portfolio contains the APO-Telyt-M 1:3,4/135.
I own and use two 135mm lenses. The Elmarit R 135mm (11211), and the Leitz Elmar-M 135mm f4 11850. They can be bought for peanuts, and they deliver great results, especially the 11211.
Using a 135mm on a rangefinder is a bit tricky. I spray and pray. On my R (and Leicaflex SL), the 11211 is a delight. No idea why they trade for around EUR 200 (give and take), maybe in 10 years people will say "oh if I only had bought one when they were cheap". They are from Walter Madler's prime years. I have actually thought about buying a second one, because they are make great pics, look and feel good, and cost almost nothing (in Leica's framwork).
So - long story short, if you are looking for an affordable 135mm, Elmarit R 135mm (11211) is your friend. Happy to send you sample pics if you PM me.
PS: Maybe this is a bit like bicycles' wheel sizes. From 26" to 29" to 27.5", with a lot of folklore and snake oil legends. Luckily, Leica's R system has 50, 60, 80, 90 and 100mm lenses (and many below 50 and above 135), so nobody has to go to bed without having their dinner.