I fully believe this software could've been written correctly by a single person; just one who knows the simplicity of the requirements and isn't trying to show

I fully believe this software could've been written correctly by a single person; just one who knows the simplicity of the requirements and isn't trying to show off with complexity. If you've written safety-critical code then you've probably worked in an industry that tries its hardest to dilute and reduce responsibility, and while imposing onerous processes may help, it doesn't fix the underlying problem.