Graphics code has a long history of memory unsafety, in more recent years causing serious security issues when we tried to put OpenGL on the web with WebGL, resulting in every device driver bug turning into a kernel-level vulnerability in the JS code. You've got a lot of people writing code with more brains than discipline [1], writing in an environment where performance is priorities one, two, and three, writing in memory unsafe languages... yeah, memory unsafety in rendering code been a big problem for a long time.

[1]: One of the most dangerous types of coder there is is the brilliant one, who has several times the working memory capacity of a normal person, and who can write 1000-line "functions" without breaking a sweat, and builds entire codebases out of such things. (Sometimes, perhaps the core loop of a program will be a bit of a monster, but the whole program isn't like that.) The cost of salvaging such things can be disturbingly close to the cost of rewriting such things, and indeed, the process for either may not be all that different.

Rust is more than just memory safety. For example, it also enables safe concurrency, which sounds like something you would want in a renderer.