Many people think that the best thing for projects like this is to have as many entities involved as possible. Anything that is controlled by single entity is bound to forget the needs of others.
For example: neither Mozilla nor Amazon might have Embedded Systems as a core interest, so they will forget about it and might accidently make decisions that ate bad for this use cases. If you also have ARM, Microcontroller vendors and so on on board, they will make sure that this topic isn't overlooked.
>> Anything that is controlled by single entity is bound to forget the needs of others.
That is perhaps the biggest concern.
When a large tech company controls governance, their needs and priorities come first.
We have seen similar concerns with other programming languages in the past: Java (Sun / Oracle), Go (Google), Swift (Apple).
Exclusive or dominant control is not necessarily bad (depends on how transparently the governance process runs and who is involved), but it can severely limit the programming language community's effect and leave the needs of some groups unfulfilled.
Would it be better if Rust was a part of the Apache foundation?