Computer systems didn't talk to each other in the early days of computing. Even the various computer lines made by the same company often needed interpreters, and forget any interoperability of systems by different vendors!
In addition, operating systems very often performed only limited tasks, and only on the machines for which they were written. If a business upgraded to a bigger, more powerful computer, the old operating system probably wouldn't work on the new computer, and often the company's data had to be entered -- again -- into the new machine.
To try to develop a convenient, interactive, useable computer system that could support many users, a group of computer scientists from Bell Labs and GE in 1965 joined an effort underway at MIT on what was called the Multics (Multiplexed Information and Computing Service) mainframe timesharing system.
All seemed cool, but Dennis had just busted out writing the entire C programming language (it is debatable whether C is still the greatest programming language ever written), and was tired of screwing around with assembly language and teams. He called up his hombre Ken Thompson (who wrote ed, which is what vim is based on), and they slammed some beers, decided to GTFO, and just knocked out writing an entire operating system. Not really a big deal, except it involves Building a Kernel, in a new language from scratch.
They also wrote a few other little programs like the Bourne Shell, which is what Bash is based on, Awk, Sed, and about 50% of what we'd now consider "basic tools" used in Linuxland and BSD (which are both Unix-like systems). Much of their work is still in use today, as we haven't really done anything in the last 40 years to top these guys. For that, we at the BBQ salute you, you crazy cli-astronauts.
"UNIX is very simple, it just needs a genius to understand its simplicity."-Dennis Ritchie
"Another danger is that commercial pressures of one sort or another will divert the attention of the best thinkers from real innovation to exploitation of the current fad, from prospecting to mining a known lode." - Also Dennis Ritchie