This was back in a time when one guy could be familiar with every single line of code running on a computer, from user space programs right down to the kernel. This level of simplicity surely did wonders for reliability. Not to say you couldn't achieve good results with a more complex modern system, though to spend a lot more time making things failsafe.
> This was back in a time when one guy could be familiar with every single line of code running on a computer, from user space programs right down to the kernel.
This is still possible, by the way. Humanity hasn't lost the ability to create simple computers. :) We just see less of them because the complex ones are more useful for day-to-day life.