The reality is, it is the right to collectively bargain that is keeping the workers from storming his house in the middle of the night and slitting his throat.
If he wants to destroy the NLRB, have fun. It'll be his death warrant he's signing.
High degree of unionization (90%+), no state interference in negotiations between worker unions and employer unions, fixed term 4 year collective agreements, a broad understanding by both workers and employers that everyone has an interest in a strong economy and a flexible work market.
The state can of course intervene. Happens quite often when essential workers go on strike like medical workers, law enforcement and if teachers go on strike for too long.
So you can in theory go on an indefinite strike, but the state can swoop in an decide what the new number is. In Norway we can it "tvungen lønnsnemnd", which can be translated to "forced pay agreement".
Nobody wants this, but it happens. In some occupations more than others.
It varies a bit from country to country, but the overall idea is that cooperation between strong national labor unions, employers and the government can lead to a solid wellfare state for all. Some parts of our workers rights are therefore kept in collective agreements instead of laws. This is of course not a perfect system, and we regularly have problems with locally sourced super-rich as well, but most people here agree it creates a better society, even for "regular" millionaires.
One of the cornerstones for this to work is strong nationwide unions to create a sane balance of power. Much of this current conflict could be solved if someone got through to Musk that the right to organize is holier to us in the nordics than gun rights are to Americans.
It is important to see both sides here though: How is he supposed to maximally exploit his wage slaves when they are allowed to organise and offer resistance to being exploited? Hmm?