You need a large enough population of skilled programmers that you can reasonably count on finding enough that are ready to move on and good enough for your project, and enough ongoing projects to keep them all busy. The number of companies that have little projects doesn't figure, nor the size of the companies. A list of big companies using it is actually the least informative, because all it takes is one person using, out of the many thousands there, to say "the company" is using it.

It would be surprising if there were two hundred paid Rust jobs already, and astonishing if there were a thousand. It needs to get to a hundred times that to have a chance to survive, and in only a few years. Ada got there and died anyway.