Sony really had a smash hit with the Walkman. They thought it was going to flop when they considered it for the mass market. They figured that people wanted to share their music not listen in isolation. They had their fair share of opportunities that they lost out on in the past do to poor decisions and the lack of fully grasping what consumers wanted but the Walkman saved them.
I always tended to gravitate towards Sony when it came to portable music...not so much with their boomboxes. While others followed suit with portable cassette players, it's hard to beat the inventor. IMO Sony had the edge of having the most reliable portable machines.