Tarnish is not the right word. Heathkit had its beginnings in aviation and developed into electronics kits after WW II. Electronics equipment was generally assembled by hand until the late 60's or so, and there were substantial savings to the customer if he/she was willing to assemble it him/herself. Then, printed circuit techniques and especially integrated circuits and automatic (and off-shore) assembly reduced the labor cost dramatically. It was technically harder to build competitive gear at home, and the labor savings are now probably negative. Kit building is much less interesting now, except for specialized market niches.
So the Heath company was bought by Zenith and eventually left the general consumer electronics business entirely. (Zenith used to be a famous brand, by the way. It could have been on the list.) A company needs to seek the most profitable markets. It's sad, but it's not a moral decision. Change is not "tarnish".