Keep in mind, Oracle was designed to run with 128KB of RAM (no swapping). So it was really tens of thousands of lines, not millions.

Was it actually that uncommon back then? My understanding is that there were other things (including Unix itself, since it predated C and was only rewritten in it later) written in assembly initially back in the 70s. Maybe Oracle is much larger compared to other things done this way than I realize, or maybe the veneration of Unix history has just been part of my awareness for too long, but for some reason hearing that this happened with Oracle doesn't seem to hit as hard for me as it seems for you. It's possible become so accustomed to something historically significant that I fail to be impressed by a similar feat, but I genuinely thought that assembly was just the language used for stuff low-level for a long time (not that I'm saying there weren't other systems languages besides C, but my recollection is having read that for a while some people were skeptical of the idea of using any high-level language in the place of assembly for systems programming).