Linotype didn’t come out of nowhere either. Printers used to cast type manually.
And don’t just gloss over TeX’s astounding correctness. It’s a truly remarkable feat of the human intellect to design something so large with so few errors.
For those who haven't seen Knuth's own analysis of his errors while writing TeX, it's well worth reading his 1989 article "The Errors of TeX" [1] and glancing through the full chronological list of errors [2].
And don’t just gloss over TeX’s astounding correctness. It’s a truly remarkable feat of the human intellect to design something so large with so few errors.