As far as I know, Topcon went out of business years ago. It was probably due to business considerations.
When I bought my first 35mm camera in the early 70's, the camera store I went to had three brands I looked at, all of them well respected and well known--Minolta, Miranda and Mamiya-Sekor. I bought a Mamiya-Sekor. Now Minolta and is Konica-Minolta, Mamiya no longer makes 35mm and Miranda is long gone.