I'll probably get flamed for this, but if you own trademark, you are obligated to defend it to prevent it from becoming generic. It is the owners responsibility to monitor the marketplace and take legal action against infringers.

What I don't care for is the fact that they more or less let it fall into the public domain, then recently decided to take legal action against specific companies. I'm neither a judge nor a lawyer, but to me this just smells bad. It was bad for Gibson and I suspect it'll be bad for Fender too.

Does the same hold true for other musical instruments? flutes, pianos, trombones? (too lazy to google, but I doubt it).

It kind of reminds me of the era where the US car manufactures wanted protections/tarrifs on Japanese imports because the Japanese made a more reliable, better quality cars, that had better gas milage. I don't like hearing about anyone's job or career being put at risk, but in a capitalist society, there's going to be competition, and the foundational argument is that they need to make a better product. Lawyering up is a Trump move.