... All of which are researched with proof of concepts. Followed by some small trials. And finalized with one or two actual rewrites of non-critical software.

I'm not saying that all companies do it this way, and that there is no "resume building" or "magpie-ing" by some engineers in many companies. But it is perfectly possible to state a thesis "Rust is better for our X and Y and probably for Z". and to then research and prove that thesis.