The best thing Rust has over Ada (no one writes ADA any more :) ) is momentum.

Although Ada has eventually got an open source compiler, and there are still around 5 vendors available, due to the way it got sold, its key use has been in the area of High Integrity Computing.

So unless that is the domain of the work, where no errors are allowed, which could possibly lead to loss of human lives, very few care of using Ada.

For the young generations, Ada is kind of something they hear it existed but they never seen live, even though it has enjoyed a regular presence at European FOSS conferences like FOSDEM.

So by being modern, Rust can appeal more to the younger generations, also some type system safety rules of Rust for parallel code can only be coded in Ada via SPARK.