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Before Multics there was chaos, and afterwards, too
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.
Over time, hope was replaced by frustration as the group effort initially failed to produce an economically useful system. Bell Labs withdrew from the effort in 1969 but a small band of users at Bell Labs Computing Science Research Center in Murray Hill -- Ken Thompson, Dennis Ritchie, Doug McIlroy, and J. F. Ossanna -- continued to seek the Holy Grail.