> Credit card transactions and banking software run on this model for example

Eh, they can but even a couple of decades ago there was a shift to open platforms. 90s and early 00s, sure, it was mainframe and exotic x86 species like Stratus machines. But even then the power of “throw a ton of cheaper Unix at it” was winning.

Banks’ central systems maybe, I have less experience there. IBM did also try for a while to ride the Linux virtualisation wave as well, saying “hey, you can run thousands of Linux instances on a single mainframe”, and I did some work porting IBM software to s390 Linux around 2007.

x86 servers weren't that common in the 90s and early 200s, that was all sun or the other commercial unix peoples things