Ada was also easy to read

Like Cobol, Ada uses full English words (Procedure <name> to declare a procedure, start to start it, end <name> to end it. Loops are surrounded by "loop" and "end loop"). It was designed (like Cobol) for readability. https://www.adaic.org/advantages/ada-overview/ for some information on the design.

I like design for readability - it makes maintenance much easier (IMO). Comments are nice, but can get out of sync with the actual code if the programmers editing code don't update the comments. Also, design for readability, IMO, makes it easier to learn the language. You're already familiar with the words. Someone with computer programming skills but know knowledge of Ada can probably figure out what a program does, because of the readability.

I'm not familiar with Rust other than what I've read on websites like lwn.net, but in terms of some of the core design, from what I've read, they're similar. Avoid "Undefined Behavior." Check up front for issues (at compile time). Define "correct behavior" specifically, and make it hard to not do the right thing. Design for guaranteed behavior.

Unfortunately, initial compilers were slow, and slow to improve, due to various reasons (including, as I recall, mandatory compliance testing before you could use the name).