I respectfully disagree, emphasis on respectfully. C++ absolutely does have Rust beat on dev speed on flexibility. I would much rather prototype a quick and dirty gameplay slice in C++ over Rust, and I think so would most people. That flexibility comes at a cost, of course. C++ is three languages in a trenchcoat, waiting for you to turn away so it can bash you over the head and mug you.
There are ways to do anything in Rust, but that doesn't change the fact that it's a language less suited for fast iteration than many others. It's a good tool, just not the best tool for this particular job, and there's no obvious reason to use it over those tools that are a better fit. For the vast majority of games, something like C# is going to make rapid prototyping far easier than either Rust or C++, with far less overhead (overhead = time = money, and gamedev is a pretty cutthroat business).
Rust's community is not particularly small, all things considered, and even adjusting for size, Rust really does under-perform in gamedev. Rust's definition of 'technical excellence' often revolves largely around memory safety, which is something I definitely want from my air traffic control systems, but which barely matters in gamedev at all. There are other things that constitute technical excellence in gamedev, and these tend to be difficult or undesirable in idiomatic Rust (often precisely because they prioritise other goals over memory safety). Rust is a fine language, I'm fairly fond of it, but it's just not a good fit for this use case. And indeed, we see the consequences of that bear out in practice.
(I'd also encourage you to read the comment thread I link above - lots of experienced people agree on this one.)