No one codes in C without realizing memory management and buffer overruns is a problem
Indeed, the vast majority of people that still program in C realize buffer overruns are an issue, and that dangling pointers are an issue.
That doesn't mean they don't occasionally one out of million times forget to bounds check something, or accidentally miss a path where something "should" be retained but isn't. Or know that some value won't overflow, but missed elsewhere where some value gets multiplied and overflows something so it becomes vastly negative, and then gets added to something else and we allocate the wrong number of bytes for something. People are bad at being consistant.
I know, I use to (a decade+ ago!) be one of the people that did security audits of iOS code.
Of corse I'm exaggerating a little: a lot of people do program in C and when you find a buffer overflow, or more frequently an unchecked numeric overflow/underflow and bounce a code change because of it they complain "that isn't a security problem! you can only reject us for security problems! show how that particular overflow/underflow is a security issue!" (I'm pretty sure not all overflows are exploitable, and the effort differential between merely finding some place that something gets multiplied and can overflow and proving that number eventually is used in away that misallocates a buffer is pretty large...but at least at that point in time we could bounce any code that had "questionable practices" even if we didn't come up with a direct exploit)
I mean look at how frequently iOS gets "jailbroken", isn't each one of those someone who knew that something should be secure missing a way in which it wasn't?
I don't doubt that Rust has its flaws, but I would expect Rust code to have fewer memory exploits then C code written by good programmers and audited by good security experts. I would expect Rust writer by good coders and also audited by security experts to have even fewer issues. (I mean Rust doesn't make sure your RNG is good, and not all security issues are memory and overflow related)