They're the same thing.

Cristal mass is "if everyone would just".

Legislation largely works because those subject to it largely agree to abide.

If everyone would just agree to stop using the old thing / start doing the new thing.

I'm not following. Everyone agrees that smart (surveillance) TVs suck but nobody is willing to take their money elsewhere. I'm the only person, in my social circle, who cares about this issue. How do we get to a critical mass of people when we are starting from essentially 0?

I think it takes time.

Critical mass is "if enough people would just"

Other stuff, like communism, really requires "if everybody would just". An arbitrarily small number of defectors will make the system tip towards collapse.